Considering Doing a Starfish Nutritional Study

[livinlifeinBKK]

Just an idea but I now have a newly vacated 20 gallon tank and was thinking about carrying out a controlled experiment regarding starfish nutrition using it as the holding tank. The starfish species could be Fromia indica stars since I have easy access to them. I could buy a few of them about the same size and give each one a different mark on an arm to differentiate between each one and use a 20 gallon tank to house them together. The tank would contain sand and live rock from the ocean. One star could be given supplemental feedings of oysters once a week, one could be removed from the main tank for one day a week and placed into a smaller tank where biofilm growth on live rock is aided with a flocculant, and the other could be the control group that receives no supplemental feedings and is just grazes on anything growing on the rocks in the 20 gallon tank. Growth could be measured by weight and tracked every 2 weeks or monthly to determine the effect of the varying diets on growth and presumably health. Additionally, two stars could be used for each feeding regimen to increase likelihood effects observed are diet based. The question is "can spot feeding a diet of oysters or biofilm in which growth is artificially accelerated sustain and/or accelerate growth in Fromia indica starfish (which eat a majority of natural biofilm in the wild)"? My hypothesis is that one of the 3 groups (probably the group being fed oysters) will grow at a faster rate. The purpose of the experiment is to develop a feeding regimen that would enable starfish to be kept in smaller tanks successfully. If significant growth is shown in the group eating the oysters or the group being fed the biofilm grown an accelerated rate through use of a flocculant like Zeovit Zeofood Plus vs. the control group, then we can conclude they're able to derive enough nutrition from these foods and therefore would not perish due to starvation as is commonly the accepted reason starfish require such large systems. I'm trying to find a way starfish can be kept in smaller tanks and for that we need to know if supplemental feedings are sufficient to sustain them or if the biofilm they normally eat must naturally form at a natural rate. I know this experimental design is far from perfect because I just came up with it yesterday but what do you guys think so far? Btw, I put it here instead of the experiment section because if I posted it there it wouldn't show up on the general forum list.

 

[ISpeakForTheSeas]

Three issues come to my mind:
1 ) You would need three separate tanks setup as close to exactly the same as possible for this to really tell us much. The reason I say this is because, if you’re keeping all of them in the same tank, any that grow faster/decline slower than the others may just be eating a limited, more nutritious food available in the tank than the others, or eating what little food is available while the others get none. If you start with three tanks with as close to the same setup as possible, then (while there may still be differences in biofilm quality/quantity in each tank) any differences would be minimal.

2 ) I really doubt 20 gallons would be enough to provide adequate food from rock to six Fromia stars. Like land bound livestock (sheep, cattle, etc.), they likely need a relatively set amount of food which may only be provided by a relatively set amount of property/real estate (pasture for land livestock, rocks or sand for marine). In my experience, the ratio of land to animal required to keep an animal properly fed is almost always higher than one (or at least I) would anticipate.

3 ) With regards to the food, weight, and nutrition: even if the starfish eats the other foods, and even if the starfish puts on more weight than the other stars in the timeframe of the study, we won’t really know if it nutritious for the star or not until the end of all of the stars’ lives, when we could compare differences in health, development (this would better studied with larval rearing), and longevity based on diet. If the star is able to live for the same duration as a wild star of the same species or longer on the diet offered, then we could declare it nutritious. Otherwise, if it dies prematurely, we have to accept that malnutrition or starvation may be - at least partially- to blame. That goes for each of the three suggested diets above. (This reminded me of finding out that deer can die of starvation with a full stomach in the winter because their bodies - adapted to having little food throughout the winter - can’t digest hay, corn, or similar crops during the winter. They have to slowly build up the bacteria in their guts by eating their more standard winter forage items before they are able to digest these things successfully).

TLDR; problem one, confounding variables from sharing the same tank and not offering three separate, uniform environments. Problem two, amount of feed. Problem three, nutrition of feed.

I’m not trying to discourage you here - I actually really appreciate seeing you try to figure out proper starfish husbandry requirements - but these are the issues/limitations that I see.

 

[livinlifeinBKK]

Three issues come to my mind:
1 ) You would need three separate tanks setup as close to exactly the same as possible for this to really tell us much. The reason I say this is because, if you’re keeping all of them in the same tank, any that grow faster/decline slower than the others may just be eating a limited, more nutritious food available in the tank than the others, or eating what little food is available while the others get none. If you start with three tanks with as close to the same setup as possible, then (while there may still be differences in biofilm quality/quantity in each tank) any differences would be minimal.

2 ) I really doubt 20 gallons would be enough to provide adequate food from rock to six Fromia stars. Like land bound livestock (sheep, cattle, etc.), they likely need a relatively set amount of food which may only be provided by a relatively set amount of property/real estate (pasture for land livestock, rocks or sand for marine). In my experience, the ratio of land to animal required to keep an animal properly fed is almost always higher than one (or at least I) would anticipate.

3 ) With regards to the food, weight, and nutrition: even if the starfish eats the other foods, and even if the starfish puts on more weight than the other stars in the timeframe of the study, we won’t really know if it nutritious for the star or not until the end of all of the stars’ lives, when we could compare differences in health, development (this would better studied with larval rearing), and longevity based on diet. If the star is able to live for the same duration as a wild star of the same species or longer on the diet offered, then we could declare it nutritious. Otherwise, if it dies prematurely, we have to accept that malnutrition or starvation may be - at least partially- to blame. That goes for each of the three suggested diets above. (This reminded me of finding out that deer can die of starvation with a full stomach in the winter because their bodies - adapted to having little food throughout the winter - can’t digest hay, corn, or similar crops during the winter. They have to slowly build up the bacteria in their guts by eating their more standard winter forage items before they are able to digest these things successfully).

TLDR; problem one, confounding variables from sharing the same tank and not offering three separate, uniform environments. Problem two, amount of feed. Problem three, nutrition of feed.

I’m not trying to discourage you here - I actually really appreciate seeing you try to figure out proper starfish husbandry requirements - but these are the issues/limitations that I see.

No, I don't find this in any way discouraging! The funny thing is that I actually posted the same post on Humblefish site and he seemed to see ensuring the same quantity of food in each tank to be a flaw actually which is why I proposed using a single holding tank and fresh live rock from the ocean could be added periodically to replenish food supply in the holding tank.

Now that I have this vacated 20 gallon tank and have done literally a ton of research into starfish biology I'd really like to be able to work with them. The Fromias here are about $10-$12 each and readily available (along with a couple species of Linckia) which is why I'd like to use them. Do you have suggestions for a study I could carry out that would be worthwhile?
Btw, my Fromia star in my other tank is still doing great! He's active and I spot feed him. No signs of regression or I'll health after 6 months!

 

[livinlifeinBKK]

After endless hours of research into the biology of starfish I would really want to "get my hands wet" and work with them. I know the study I proposed has holes in it and would be no simple feat so does anyone else have any study suggestions I can carry out with these incredible animals that would further our knowledge of husbandry or anything research at all I could do involving stars? I'm open to all suggestions.

 

[ISpeakForTheSeas]

No, I don't find this in any way discouraging! The funny thing is that I actually posted the same post on Humblefish site and he seemed to see ensuring the same quantity of food in each tank to be a flaw actually which is why I proposed using a single holding tank and fresh live rock from the ocean could be added periodically to replenish food supply in the holding tank.

Now that I have this vacated 20 gallon tank and have done literally a ton of research into starfish biology I'd really like to be able to work with them. The Fromias here are about $10-$12 each and readily available (along with a couple species of Linckia) which is why I'd like to use them. Do you have suggestions for a study I could carry out that would be worthwhile?
Btw, my Fromia star in my other tank is still doing great! He's active and I spot feed him. No signs of regression or I'll health after 6 months!

They might have thought that by giving each access to the same food in the same tank that they would have equal opportunity to eat the same quality of food in the same quantity, but that would actually be incredibly difficult to ensure (you would literally have to control everything that goes in the tank from bacteria to diatoms and dinoflagellates to pods, etc. so that you know the food is the same throughout, and you would want a much larger sample size to account for individual differences).

Glad to hear your star is doing well! Hopefully they continue to for many years to come.

As far as studies you could do with them go, it depends a bit on your available resources. One relatively easy study would be figuring out preferred supplemental foods (put one food option - such as a specific species of oyster - on one side of the tank and another food option - such as a specific brand of pellet food - on the other, then put the star in the middle between the two and record which - if any - of the two it goes for. If it eats one over the other, keep the one that is preferred and test it against another food - such as a specific species of snail - and record the preferred food again). Once a preferred supplemental feed is found over a number of different options, you can try using it long term to see if it improves the captive survival lifespan of the stars. Of course, this may or may not improve the lifespan, but it's an easy one that might help.

Another similar study you might be able to do that may potentially be more helpful (especially if you have access to a lab where you could get clear pictures of/ID's for individual species of microscopic creatures): you could gather, in separate containers, a bunch of live rock (hopefully) with different biofilms on them, and put a bunch of clean, dry rock (and/or other media) in each of the containers. The goal would be to let the biofilm on the live rock culture on the new, dry media (thus producing more of the same biofilms), and then you would test for feeding preferences like in the study above (i.e. food options on opposite ends of the tank, the star in the middle, see what gets eaten, repeat with the winner and a new alternative option). With this, you could not only figure out a good deal about biofilm preferences of the stars, but you could also test to see if they have preferred timeframes for different biofilms (i.e. since biofilm composition changes over time, you could not only test each of the films against each other - film x against film y, for instance - but you could also, for example, test film x at two weeks of biofilm formation against film x at four weeks or six weeks of biofilm formation too). If you have access to a lab (as mentioned above) you could potentially figure out the composition of the biofilms being eaten, and therefor figure out exactly what we need to be able to replicate to feed these guys. Again, once a clear preference has been found, you would keep at least one star on it long term to see how it impacts the star's captive lifespan (the more the merrier).

Along the same lines as the above, you can test for feed preferences with various sponges (species ID's are likely to be difficult, but necessary for the study to be useful, so again, access to a lab would be helpful) or ascidians (tunicates) or nuisance algae or whatever. The sponges would likely (but not necessarily) be the most useful to study though.

Again, the more stars you can test these with, the better, but the main thing would be to find the preferred food and study it for a long term diet. As mentioned above, the more uniform the situation, the better (and, while it wouldn't necessarily mean anything without long term success backing it, I still would recommending measuring oral/central disk and leg length and weighing the stars used, as this - if backed by long term success - could be useful information for studies in the future).

Those are the studies that come to mind at the moment. If I can think of any more, I'll let you know.

 

[livinlifeinBKK]

They might have thought that by giving each access to the same food in the same tank that they would have equal opportunity to eat the same quality of food in the same quantity, but that would actually be incredibly difficult to ensure (you would literally have to control everything that goes in the tank from bacteria to diatoms and dinoflagellates to pods, etc. so that you know the food is the same throughout, and you would want a much larger sample size to account for individual differences).

Glad to hear your star is doing well! Hopefully they continue to for many years to come.

As far as studies you could do with them go, it depends a bit on your available resources. One relatively easy study would be figuring out preferred supplemental foods (put one food option - such as a specific species of oyster - on one side of the tank and another food option - such as a specific brand of pellet food - on the other, then put the star in the middle between the two and record which - if any - of the two it goes for. If it eats one over the other, keep the one that is preferred and test it against another food - such as a specific species of snail - and record the preferred food again). Once a preferred supplemental feed is found over a number of different options, you can try using it long term to see if it improves the captive survival lifespan of the stars. Of course, this may or may not improve the lifespan, but it's an easy one that might help.

Another similar study you might be able to do that may potentially be more helpful (especially if you have access to a lab where you could get clear pictures of/ID's for individual species of microscopic creatures): you could gather, in separate containers, a bunch of live rock (hopefully) with different biofilms on them, and put a bunch of clean, dry rock (and/or other media) in each of the containers. The goal would be to let the biofilm on the live rock culture on the new, dry media (thus producing more of the same biofilms), and then you would test for feeding preferences like in the study above (i.e. food options on opposite ends of the tank, the star in the middle, see what gets eaten, repeat with the winner and a new alternative option). With this, you could not only figure out a good deal about biofilm preferences of the stars, but you could also test to see if they have preferred timeframes for different biofilms (i.e. since biofilm composition changes over time, you could not only test each of the films against each other - film x against film y, for instance - but you could also, for example, test film x at two weeks of biofilm formation against film x at four weeks or six weeks of biofilm formation too). If you have access to a lab (as mentioned above) you could potentially figure out the composition of the biofilms being eaten, and therefor figure out exactly what we need to be able to replicate to feed these guys. Again, once a clear preference has been found, you would keep at least one star on it long term to see how it impacts the star's captive lifespan (the more the merrier).

Along the same lines as the above, you can test for feed preferences with various sponges (species ID's are likely to be difficult, but necessary for the study to be useful, so again, access to a lab would be helpful) or ascidians (tunicates) or nuisance algae or whatever. The sponges would likely (but not necessarily) be the most useful to study though.

Again, the more stars you can test these with, the better, but the main thing would be to find the preferred food and study it for a long term diet. As mentioned above, the more uniform the situation, the better (and, while it wouldn't necessarily mean anything without long term success backing it, I still would recommending measuring oral/central disk and leg length and weighing the stars used, as this - if backed by long term success - could be useful information for studies in the future).

Those are the studies that come to mind at the moment. If I can think of any more, I'll let you know.

I attend a university and might be able to get access to a good microscope but I'm not sure how I would go about identifying all the microorganisms on the live rock due to the sheer number of microorganisms present. I like your idea of testing the rocks with biofilm growth of different ages and find that interesting. What size tank would be necessary for this type of experiment involving placing the star in the middle and letting it choose which food it prefers? My concern here is that I'm not sure at what distance they can sense foods (especially different biofilm compositions).

 

[ISpeakForTheSeas]

I attend a university and might be able to get access to a good microscope but I'm not sure how I would go about identifying all the microorganisms on the live rock due to the sheer number of microorganisms present. I like your idea of testing the rocks with biofilm growth of different ages and find that interesting. What size tank would be necessary for this type of experiment involving placing the star in the middle and letting it choose which food it prefers? My concern here is that I'm not sure at what distance they can sense foods (especially different biofilm compositions).

Honestly, I wouldn't bother trying to ID them all until you've found a clearly preferred biofilm, and my recommended method for ID'ing them after that (the lazy method) would be to take a lot of good, clear, microscope pictures of the winning film, and send them to a bunch of different marine biologists (preferably those who study marine bacteria and/or other marine microorganisms, or those who study starfish) informing them what is in the picture and asking for help to ID the various organisms. If you let them know your starfish prefers this specific composition (as confirmed by your testing) and that you'd like to know what is in it so you could inform people what this specific species eats and allow them to replicate it accurately (should the star live a decent length of time on the diet), you'd likely find a helping hand or two.
Edit: just adding here that you would try to get photos of both the biofilm as a whole, and each individual species involved in the biofilm. That way you could send out photos of the specific specimens you need help ID'ing, and you wouldn't necessarily overwhelm everyone with the sheer volume of pictures/specimens you need help with (you could eliminate certain photos from being sent as you confirm the ID of the specimens in them).

I'm not sure what size of tank would be needed (the only stars I know this sort of testing has been done with were juvenile COTS in little pots). I'd imagine they could find the food from one end of the twenty gallon to the other, but I don't know for certain (you could also experiment with that). That said, if you put the food so that each item would be (for example) 3 inches away from the star in opposite directions when you put the star in the tank, it should be able to find them both without issue.

 

[livinlifeinBKK]

Honestly, I wouldn't bother trying to ID them all until you've found a clearly preferred biofilm, and my recommended method for ID'ing them after that (the lazy method) would be to take a lot of good, clear, microscope pictures of the winning film, and send them to a bunch of different marine biologists (preferably those who study marine bacteria and/or other marine microorganisms, or those who study starfish) informing them what is in the picture and asking for help to ID the various organisms. If you let them know your starfish prefers this specific composition (as confirmed by your testing) and that you'd like to know what is in it so you could inform people what this specific species eats and allow them to replicate it accurately (should the star live a decent length of time on the diet), you'd likely find a helping hand or two.
Edit: just adding here that you would try to get photos of both the biofilm as a whole, and each individual species involved in the biofilm. That way you could send out photos of the specific specimens you need help ID'ing, and you wouldn't necessarily overwhelm everyone with the sheer volume of pictures/specimens you need help with (you could eliminate certain photos from being sent as you confirm the ID of the specimens in them).

I'm not sure what size of tank would be needed (the only stars I know this sort of testing has been done with were juvenile COTS in little pots). I'd imagine they could find the food from one end of the twenty gallon to the other, but I don't know for certain (you could also experiment with that). That said, if you put the food so that each item would be (for example) 3 inches away from the star in opposite directions when you put the star in the tank, it should be able to find them both without issue.

How would you aquascape the tank? If the goal is to offer the stars only 2 choices to choose from to eat to show preference how should the tank be aquascaped so that they don't feed off of the other live ocean rock in the tank or should it be dry rock?

 

[gbru316]

How would you aquascape the tank? If the goal is to offer the stars only 2 choices to choose from to eat to show preference how should the tank be aquascaped so that they don't feed off of the other live ocean rock in the tank or should it be dry rock?

im not sure it’s possible to grow 2 different films in the same tank due to the mobility of bacteria.

but that presents challenges because different tanks means less control of the experiment.

You might be able to get away with 2 tanks, a shared sump, and high wattage UV sterilizer on the return. And, of course, rigorous physical isolation methods to prevent any drop of water transfer between the two tanks.

 

[livinlifeinBKK]

T

im not sure it’s possible to grow 2 different films in the same tank due to the mobility of bacteria.

but that presents challenges because different tanks means less control of the experiment.

You might be able to get away with 2 tanks, a shared sump, and high wattage UV sterilizer on the return. And, of course, rigorous physical isolation methods to prevent any drop of water transfer between the two tanks.

He tanks would be completely separate systems

 

[ISpeakForTheSeas]

How would you aquascape the tank? If the goal is to offer the stars only 2 choices to choose from to eat to show preference how should the tank be aquascaped so that they don't feed off of the other live ocean rock in the tank or should it be dry rock?

Fair question, and I'm not sure what the best answer for it is. I would guess you would either want to try and fence off the rock so the stars can't get to it but you can still benefit from the biofilter it offers, avoid adding rock altogether (either running sand without rock, or just bare-bottom) by seriously oversizing the filtration, or to do dry rock to try to minimize any potential confounding variables as discussed above. (Or a combination of the first and third.) If you want to fence it off, you basically just need to have it separated from the stars in such a way so as to prevent them from feeding off of any algae or other things that may grow on the rocks.

What I do know, however, is that, usually, with these sorts of experiments, they starve the specimens for a few days (three seems to be a pretty typical number) before placing them in with the food. So, you'd want to grow all of the feeds out in separate tanks, and have a little tank/container (separate from the one the stars live in) to test the feeding preference in (i.e. have one container for the stars, one for each of the food options, and one where you put one star and two different food options when it's feeding time - you'd need to either add the foods first and the star second, or add both the foods at the same time after adding the star). This would pretty well minimize/avoid the issues grbu316 pointed out above, as the situation would be as close to the same as you could get it for each of the stars studied. The containers for the feeds and for the testing don't have to be real tanks - they basically just need to be properly sized, non-toxic containers of either glass or the same different material that you can add saltwater, light (if needed), and a bubbler to. After each feeding you would want to clean the food preference test tank and just refill it before each use with new saltwater for the next test.

Edit: the tanks would likely need heaters too.

 

[livinlifeinBKK]

Fair question, and I'm not sure what the best answer for it is. I would guess you would either want to try and fence off the rock so the stars can't get to it but you can still benefit from the biofilter it offers, avoid adding rock altogether (either running sand without rock, or just bare-bottom) by seriously oversizing the filtration, or to do dry rock to try to minimize any potential confounding variables as discussed above. (Or a combination of the first and third.) If you want to fence it off, you basically just need to have it separated from the stars in such a way so as to prevent them from feeding off of any algae or other things that may grow on the rocks.

What I do know, however, is that, usually, with these sorts of experiments, they starve the specimens for a few days (three seems to be a pretty typical number) before placing them in with the food. So, you'd want to grow all of the feeds out in separate tanks, and have a little tank/container (separate from the one the stars live in) to test the feeding preference in (i.e. have one container for the stars, one for each of the food options, and one where you put one star and two different food options when it's feeding time - you'd need to either add the foods first and the star second, or add both the foods at the same time after adding the star). This would pretty well minimize/avoid the issues grbu316 pointed out above, as the situation would be as close to the same as you could get it for each of the stars studied. The containers for the feeds and for the testing don't have to be real tanks - they basically just need to be properly sized, non-toxic containers of either glass or the same different material that you can add saltwater, light (if needed), and a bubbler to. After each feeding you would want to clean the food preference test tank and just refill it before each use with new saltwater for the next test.

Edit: the tanks would likely need heaters too.

So equipment needed:

-20 gallon tank to hold all stars with live rock
-one container for each food option (to grow biofilm at different stages)
-one tank to place the star in for feeding time so it can choose which food source it prefers

How often will they need to be fed do you think since they won't be able to feed in the holding tank?

Also, I feel the dry rock would be very slow to be colonized even with live rock in the tank with it so should a flocculant be used?

 

[ISpeakForTheSeas]

So equipment needed:

-20 gallon tank to hold all stars with live rock
-one container for each food option (to grow biofilm at different stages)
-one tank to place the star in for feeding time so it can choose which food source it prefers

How often will they need to be fed do you think since they won't be able to feed in the holding tank?

Also, I feel the dry rock would be very slow to be colonized even with live rock in the tank with it so should a flocculant be used?

I’m honestly not sure how often they should be fed - the starfish I’ve seen this sort of thing studied with are grazers, so they’re pretty much just constantly fed unless they're being starved prior to the food preference test. Given that these guys are known grazers too, I guess you would want to take something you know they eat (I believe you are already supplement feeding your star oysters, if I remember correctly) and target feed each one once or twice daily (with equal weighted/sized portions) to start. Then, you could either pull the star from the star holding system three days before the food preference test and keep it in the testing tank until after the test is done, then re-add it to the star holding tank, or you could potentially just not target feed it for three days prior to the test (you might want to take the extra precaution of putting it in a breeder box or something if you take this route, but I worry that may cause unnecessary stress if you do so). The most important thing is just making sure that if they are eating food in the holding tank, they are all eating the same type and amount of food to try and minimize any potential confounding variables that may arise (the method of feeding I suggested above, while not perfect, should be "good enough" for your purpose here).

Once you figure out a biofilm they'll eat, I'd be tempted to say try growing out little slides or dishes or rocks of it (preferably of approximately equal size/weight) and swap those in over the oysters. Once you figure out which biofilm/age of biofilm they prefer out of all those offered to them, I'd say produce as much of it as possible and swap it out for the other biofilm/oysters (if needed), then see about how much they eat daily by offering either a ton of slides at once, or by watching and swapping out slides each time one is cleared. You will want to thoroughly sanitize each slide between feedings to prevent them being contaminated and potentially altering the biofilm structure either on themselves or in your feed grow out tanks. To be clear, I'd recommend making sure (once you have a clear winner of a biofilm) that you start multiple separate cultures of it in case one crashes, gets contaminated, changes drastically, etc.

Again, while these methods aren't perfect, they should be good enough for this study.

As far as flocculants are concerned, I'd say probably grow out a duplicate culture or two of each biofilm naturally first, then attempt adding a flocculant to one of the spare cultures to compare biofilm formation (quality) and growth rate. This way, if the flocculant throws something off in the biofilm structure, you have a spare culture to work with (which I would duplicate again). Knowing that most of these biofilm forming species are eutrophic, you might be able to speed up growth (colonization rate) just by carbon dosing and/or adding NO3 and PO4, but - again - I would experiment with this after ensuring you have a backup culture to work with.

 

[livinlifeinBKK]

I’m honestly not sure how often they should be fed - the starfish I’ve seen this sort of thing studied with are grazers, so they’re pretty much just constantly fed unless they're being starved prior to the food preference test. Given that these guys are known grazers too, I guess you would want to take something you know they eat (I believe you are already supplement feeding your star oysters, if I remember correctly) and target feed each one once or twice daily (with equal weighted/sized portions) to start. Then, you could either pull the star from the star holding system three days before the food preference test and keep it in the testing tank until after the test is done, then re-add it to the star holding tank, or you could potentially just not target feed it for three days prior to the test (you might want to take the extra precaution of putting it in a breeder box or something if you take this route, but I worry that may cause unnecessary stress if you do so). The most important thing is just making sure that if they are eating food in the holding tank, they are all eating the same type and amount of food to try and minimize any potential confounding variables that may arise (the method of feeding I suggested above, while not perfect, should be "good enough" for your purpose here).

Once you figure out a biofilm they'll eat, I'd be tempted to say try growing out little slides or dishes or rocks of it (preferably of approximately equal size/weight) and swap those in over the oysters. Once you figure out which biofilm/age of biofilm they prefer out of all those offered to them, I'd say produce as much of it as possible and swap it out for the other biofilm/oysters (if needed), then see about how much they eat daily by offering either a ton of slides at once, or by watching and swapping out slides each time one is cleared. You will want to thoroughly sanitize each slide between feedings to prevent them being contaminated and potentially altering the biofilm structure either on themselves or in your feed grow out tanks. To be clear, I'd recommend making sure (once you have a clear winner of a biofilm) that you start multiple separate cultures of it in case one crashes, gets contaminated, changes drastically, etc.

Again, while these methods aren't perfect, they should be good enough for this study.

As far as flocculants are concerned, I'd say probably grow out a duplicate culture or two of each biofilm naturally first, then attempt adding a flocculant to one of the spare cultures to compare biofilm formation (quality) and growth rate. This way, if the flocculant throws something off in the biofilm structure, you have a spare culture to work with (which I would duplicate again). Knowing that most of these biofilm forming species are eutrophic, you might be able to speed up growth (colonization rate) just by carbon dosing and/or adding NO3 and PO4, but - again - I would experiment with this after ensuring you have a backup culture to work with.

Thanks for the detailed response! I've also gotten in contact by email with a starfish expert who's written several books on the biology of starfish and I'll run the design by him and see if he has anything to add

 

[ISpeakForTheSeas]

Thanks for the detailed response! I've also gotten in contact by email with a starfish expert who's written several books on the biology of starfish and I'll run the design by him and see if he has anything to add

Let me know what they say!

 

[livinlifeinBKK]

Let me know what they say!

I certainly will keep you informed! Most of the dry rock here that I have access to is really just live rock that's been taken out of the water and dried (maybe that's a good thing since there will be minimal dust or other unwanted contaminants on it)...how long would you guess it would take to be colonized by microorganisms if its in a 5 gallon tank with some nice ocean sourced live rock?

 

[ISpeakForTheSeas]

I would guess colonization would begin almost immediately (meaning, from what I've read, I would be surprised if there was a dry rock in the tank with no bacteria from the biofilm on it after just a few hours), but for full, initial colonization to occur, I would guess anywhere from 2-4 weeks dependent on each dry rock's level of exposure to the biofilm on the live rock (this is just a guess, however, and the actual time may be somewhat longer or shorter - though I would be surprised if it were more than a day two on the shorter side). Once fully initially colonized, I would assume the biofilm would largely follow the timeframe of that paper I shared with you in another thread (i.e. two weeks after full initial colonization to secondary colonizers becoming dominant, and another two weeks for tertiary colonizers to become dominant after that).

Also, yeah, the deader the dry rock, the better for study purposes. You may even want to consider bleaching or otherwise sterilizing the dry rock as a just in case before using them the first time (some marine organisms can go dormant under some pretty extreme conditions for some pretty long durations, then "revive" after that time, so, while quite likely unnecessary, this may be a good addition precaution to take).

 

[livinlifeinBKK]

A shop near me just got in a bunch of live rock right from the ocean...looks like pretty high quality stuff for starfish feeding...click the link to check it out

Live rock for sale

 

[AydenLincoln]

That would be an interesting experiment just probably way too expensive and has way to many variables to be super accurate just my thoughts.

 

[livinlifeinBKK]

That would be an interesting experiment just probably way too expensive and has way to many variables to be super accurate just my thoughts.

It wouldn't be too expensive...$10-$12 per Fromia and already have the tanks. The only expenses would be the rock and sand for the holding tank along with one or two supplements to use as flocculants which would be optional. Where do you see too many variables? I thought me and @ISpeakForTheSeas worked it out to be pretty simple.