Considering Doing a Starfish Nutritional Study

[Timfish]

@Timfish you're a scientific minded individual...can I have your opinion on this experimental design?

Thank you! but for the record I'm not a trained scientist, just passionate about understanding what's goin on in my tanks. As a start I'd think you should be able to get some idea of what's happening. If you see an variation you've got data to work with with to refine your expeirements and if you don't see any variation you've got data to work with to refine your expeirements. TangerineSpeedo has some good points. Documenting what you're doing is essential. To simplify maintenance and eliminate differences in water quality I think your idea of using a large tank as a refugium to keep your rock in with smaller tanks for individual stars plumbed into it is a good idea. Keeping just one starfish per tank minimizes social behavior as a variable too.

(This is off topic but this video on social structures of starfish populations is fascinating)

 

[Timfish]

These are some of the questions the starfish expert posed. Keep in mind I hadn't updated him on the most current design of the experiment but I thought you guys might like to see his questions anyway. The text at the bottom was part of my email. His response questions at the top.

For startes I would think wieging them in a known quantity of water then wieighing them out of water would give a pretty good indication of growth or loss of mass, obviously run it by your expert. His questions about biofilms and environments are more important.

 

[ISpeakForTheSeas]

I've been thinking things over today and it dawned on me that it might work better to use the 20 gallon tank for placing the live ocean rock in to grow the biofilm on the other rocks and keep the stars in smaller tanks (1 to a tank). That way the stars wouldn't have to be removed and transferred for feeding and it would solve the problem of the stars getting uneven nutrition in the holding tank. I think to ensure that the stars are getting an even amount of biofilm, the rocks should be close in weight. (That would answer the question asked by the expert regarding making sure they have access to the same amount of food.) Does it matter if the small tanks with the stars are slightly different sizes though? I don't think it does since the food will be transferred to the tanks (5 gallon vs 8 gallon or something like that). Also, since part of the purpose of the experiment is to enable us to better keep them in home aquariums, should I also give equal rations of a supplemental food source such as oysters or maybe Masstick to each star? I find it hard to believe that the biofilm will generate quickly enough to avoid starvation (although they are known to last months in small inadequate tanks so maybe that's not as much of an issue.) After all, progress will be tracked by weight.

The key with studies like this is to get and keep everything as close to the same as possible. So, here's how I would personally do it:

1 ) Stars are all kept in bare-bottom or dry-sand tanks with a shared sump/refugium (as you and Timfish suggested above) and target fed with pieces of the same food of the same weight (oysters or Masstick would both work as long as you know the stars will eat them):

These steps would eliminate issues with water quality difference between the starfish holding tanks that could be confounding variables, and they would eliminate differences in diet which could be confounding variables.

2 ) Different biofilms (as confirmed by microscope observation) are grown out in different little tanks (weighing the media [likely dry rock or something like ceramic disks] - which should be as close in size and shape and weight as you can get each piece of media to be - it is grown on in advance and weighing the media it is grown on after the biofilm has colonized it, and offering pieces which have shown similar increases in weight - the weight difference will likely be tiny, so you would need a very sensitive scale for this) and offered two at a time to a single, three-day starved, sea star in a third tank at equal distances from the star. Once the star is done feeding, I would weigh both pieces of offered media again to try and gauge how much they ate (they would be placed in the feed preference test tank for a set amount of time and removed when that time is complete - the COTS study I've read used 48 hours as the time in the test tank, so, it would depend on the initial size of the stars and the size of the media pieces used to offer food to them, but I'd probably use that timeframe too if the pieces are relatively close in size to the stars, and I would assume that the piece they go for first is their preferred film unless they ate substantially more weight wise on the other piece) :

While not perfect, this would offer a reasonable level of control to the feeding and a reasonable level of assurance that the feeds offered are of similar value (from the experimenter's perspective, not necessarily the sea star's). Additionally, by using media similar to the rock which the biofilm is originally grown on - such as dry rock or a ceramic media - you should be able to avoid issues with the biofilm having a different preferred media for growth (some prefer/grow better on rocks, some sand, some glass, some metal, some plastic, etc. - so keeping the media of a similar composition reduces the likelihood of a change in biofilm composition from rock to media).

3 ) I would weigh (I don't know if wet weight or dry weight would be better, so I'm inclined to say I would use both wet and dry as Timfish suggested above to be safe) and measure the starfish (arm length and disc diameter) at the start of the study and probably on the first day of starving every time they are starved before a feed preference test (ideally, all the stars would either be starved at the same time and preference tested the same day, or they would be tracked individually and share the same testing schedule as the others - i.e. they would all go x days being fed as normal, then starved for three days, then preference tested):

Consistency with testing like the measuring and weighing is key to good data. Record everything you can.

4 ) Once a preferred biofilm has been found using the feed preference testing, I would consider experiment number one complete, and I would begin experiment number two. Experiment number two would be run pretty much the exact same as experiment number one, but it would be using exclusively the same biofilm feed at different ages in the preference testing (i.e. I would use biofilm x at two weeks of media colonization and four weeks of colonization as the food options for the preference test - find out which is preferred of those two and then test it against biofilm x at six weeks of colonization) :

Figuring out a preferred film first and a preferred film age second would greatly simplify the testing process, but you could include different ages of films in the first experiment to see if that influences the stars' preferred film choice.

5 ) Once a preferred film age has been determined, I would consider experiment two complete, and I would move on to experiment three - determining how much of their preferred biofilm they eat on average daily as determined by weight of media offered before and after feeding. Carried out with a similar starvation then feeding method (definitely only using one star at a time for this experiment), I would starve the star for three days, then put it in the feeding experiment tank with several pieces of their preferred biofilm media (the goal would be to add more than they could realistically eat so that you can compare the before and after weight difference of the offered media at the end of the 48 or whatever hour long time period they're in the tank for and get an idea of how much they eat by weight) :

Because you'd be weighing each piece of media offered to the star before and after each feeding, you may have some idea by this point of how much they'll eat in a set amount of time - this would be trying to confirm that. There would be some error, as the biofilm could start recolonizing the cleared media in that 48 hour timeframe, but it would get you into the ballpark of how much they eat. I assume this would give a relatively accurate measure of feed consumed, but I may well be wrong - if the expert you're in contact with has better suggestions, I would love to hear them.

6 ) From here, I would be done with the starvation and feeding experiments, and I would try to figure out ways to produce enough of the preferred feed for the stars (using the starvation levels of eating as an estimated ceiling for how much they may consume daily). I would change from feeding the stars the oysters or Masstick to trying to feed them their preferred biofilm. Importantly, I would still track the weight of media offered before and after feeding to see if the stars eat less when not starved.

That's how I would do this experiment. Now, to address some other points above, you are correct that you likely wouldn't be able to produce enough biofilm feed to keep all of the stars from starving, so you may want to give some away after the tests are complete. The goal, however, would be to figure out what they prefer quickly enough that you could figure out how (if possible) to grow it in sufficient quantity to prevent their starvation. Also, until step 5, I would assume the amount of biofilm offered would be limited for feeding.

 

[livinlifeinBKK]

The key with studies like this is to get and keep everything as close to the same as possible. So, here's how I would personally do it:

1 ) Stars are all kept in bare-bottom or dry-sand tanks with a shared sump/refugium (as you and Timfish suggested above) and target fed with pieces of the same food of the same weight (oysters or Masstick would both work as long as you know the stars will eat them):

These steps would eliminate issues with water quality difference between the starfish holding tanks that could be confounding variables, and they would eliminate differences in diet which could be confounding variables.

2 ) Different biofilms (as confirmed by microscope observation) are grown out in different little tanks (weighing the media [likely dry rock or something like ceramic disks] - which should be as close in size and shape and weight as you can get each piece of media to be - it is grown on in advance and weighing the media it is grown on after the biofilm has colonized it, and offering pieces which have shown similar increases in weight - the weight difference will likely be tiny, so you would need a very sensitive scale for this) and offered two at a time to a single, three-day starved, sea star in a third tank at equal distances from the star. Once the star is done feeding, I would weigh both pieces of offered media again to try and gauge how much they ate (they would be placed in the feed preference test tank for a set amount of time and removed when that time is complete - the COTS study I've read used 48 hours as the time in the test tank, so, it would depend on the initial size of the stars and the size of the media pieces used to offer food to them, but I'd probably use that timeframe too if the pieces are relatively close in size to the stars, and I would assume that the piece they go for first is their preferred film unless they ate substantially more weight wise on the other piece) :

While not perfect, this would offer a reasonable level of control to the feeding and a reasonable level of assurance that the feeds offered are of similar value (from the experimenter's perspective, not necessarily the sea star's). Additionally, by using media similar to the rock which the biofilm is originally grown on - such as dry rock or a ceramic media - you should be able to avoid issues with the biofilm having a different preferred media for growth (some prefer/grow better on rocks, some sand, some glass, some metal, some plastic, etc. - so keeping the media of a similar composition reduces the likelihood of a change in biofilm composition from rock to media).

3 ) I would weigh (I don't know if wet weight or dry weight would be better, so I'm inclined to say I would use both wet and dry as Timfish suggested above to be safe) and measure the starfish (arm length and disc diameter) at the start of the study and probably on the first day of starving every time they are starved before a feed preference test (ideally, all the stars would either be starved at the same time and preference tested the same day, or they would be tracked individually and share the same testing schedule as the others - i.e. they would all go x days being fed as normal, then starved for three days, then preference tested):

Consistency with testing like the measuring and weighing is key to good data. Record everything you can.

4 ) Once a preferred biofilm has been found using the feed preference testing, I would consider experiment number one complete, and I would begin experiment number two. Experiment number two would be run pretty much the exact same as experiment number one, but it would be using exclusively the same biofilm feed at different ages in the preference testing (i.e. I would use biofilm x at two weeks of media colonization and four weeks of colonization as the food options for the preference test - find out which is preferred of those two and then test it against biofilm x at six weeks of colonization) :

Figuring out a preferred film first and a preferred film age second would greatly simplify the testing process, but you could include different ages of films in the first experiment to see if that influences the stars' preferred film choice.

5 ) Once a preferred film age has been determined, I would consider experiment two complete, and I would move on to experiment three - determining how much of their preferred biofilm they eat on average daily as determined by weight of media offered before and after feeding. Carried out with a similar starvation then feeding method (definitely only using one star at a time for this experiment), I would starve the star for three days, then put it in the feeding experiment tank with several pieces of their preferred biofilm media (the goal would be to add more than they could realistically eat so that you can compare the before and after weight difference of the offered media at the end of the 48 or whatever hour long time period they're in the tank for and get an idea of how much they eat by weight) :

Because you'd be weighing each piece of media offered to the star before and after each feeding, you may have some idea by this point of how much they'll eat in a set amount of time - this would be trying to confirm that. There would be some error, as the biofilm could start recolonizing the cleared media in that 48 hour timeframe, but it would get you into the ballpark of how much they eat. I assume this would give a relatively accurate measure of feed consumed, but I may well be wrong - if the expert you're in contact with has better suggestions, I would love to hear them.

6 ) From here, I would be done with the starvation and feeding experiments, and I would try to figure out ways to produce enough of the preferred feed for the stars (using the starvation levels of eating as an estimated ceiling for how much they may consume daily). I would change from feeding the stars the oysters or Masstick to trying to feed them their preferred biofilm. Importantly, I would still track the weight of media offered before and after feeding to see if the stars eat less when not starved.

That's how I would do this experiment. Now, to address some other points above, you are correct that you likely wouldn't be able to produce enough biofilm feed to keep all of the stars from starving, so you may want to give some away after the tests are complete. The goal, however, would be to figure out what they prefer quickly enough that you could figure out how (if possible) to grow it in sufficient quantity to prevent their starvation. Also, until step 5, I would assume the amount of biofilm offered would be limited for feeding.

Wow, you really have a talent for thinking ahead and being detailed with experimentation! Do you have a scientific background? Oh, and yeah, I just found out last week my star is fond of Masstick which is probably a good food source as it's easily digestible. He's eating some right now actually.

 

[ISpeakForTheSeas]

Wow, you really have a talent for thinking ahead and being detailed with experimentation! Do you have a scientific background?

The "soft-science" of psychology. I was going to go into research psychology, but after three separate classes on stats talking about ways to lie, cheat, or manipulate data to say what you (or your employer) wants it to say, I decided to switch paths.

 

[livinlifeinBKK]

For startes I would think wieging them in a known quantity of water then wieighing them out of water would give a pretty good indication of growth or loss of mass, obviously run it by your expert. His questions about biofilms and environments are more important.

I the starfish expert a link to the thread so if he has time maybe he'll be willing to read through it...btw, check out this live rock a shop just got in stock near me...it was probably in the ocean just a few days agoLive rock for sale

The "soft-science" of psychology. I was going to go into research psychology, but after three separate classes on stats talking about ways to lie, cheat, or manipulate data to say what you (or your employer) wants it to say, I decided to switch paths.

Well you certainly seem to have a talent for experimental design and I'm not just saying that!

 

[livinlifeinBKK]

The key with studies like this is to get and keep everything as close to the same as possible. So, here's how I would personally do it:

1 ) Stars are all kept in bare-bottom or dry-sand tanks with a shared sump/refugium (as you and Timfish suggested above) and target fed with pieces of the same food of the same weight (oysters or Masstick would both work as long as you know the stars will eat them):

These steps would eliminate issues with water quality difference between the starfish holding tanks that could be confounding variables, and they would eliminate differences in diet which could be confounding variables.

2 ) Different biofilms (as confirmed by microscope observation) are grown out in different little tanks (weighing the media [likely dry rock or something like ceramic disks] - which should be as close in size and shape and weight as you can get each piece of media to be - it is grown on in advance and weighing the media it is grown on after the biofilm has colonized it, and offering pieces which have shown similar increases in weight - the weight difference will likely be tiny, so you would need a very sensitive scale for this) and offered two at a time to a single, three-day starved, sea star in a third tank at equal distances from the star. Once the star is done feeding, I would weigh both pieces of offered media again to try and gauge how much they ate (they would be placed in the feed preference test tank for a set amount of time and removed when that time is complete - the COTS study I've read used 48 hours as the time in the test tank, so, it would depend on the initial size of the stars and the size of the media pieces used to offer food to them, but I'd probably use that timeframe too if the pieces are relatively close in size to the stars, and I would assume that the piece they go for first is their preferred film unless they ate substantially more weight wise on the other piece) :

While not perfect, this would offer a reasonable level of control to the feeding and a reasonable level of assurance that the feeds offered are of similar value (from the experimenter's perspective, not necessarily the sea star's). Additionally, by using media similar to the rock which the biofilm is originally grown on - such as dry rock or a ceramic media - you should be able to avoid issues with the biofilm having a different preferred media for growth (some prefer/grow better on rocks, some sand, some glass, some metal, some plastic, etc. - so keeping the media of a similar composition reduces the likelihood of a change in biofilm composition from rock to media).

3 ) I would weigh (I don't know if wet weight or dry weight would be better, so I'm inclined to say I would use both wet and dry as Timfish suggested above to be safe) and measure the starfish (arm length and disc diameter) at the start of the study and probably on the first day of starving every time they are starved before a feed preference test (ideally, all the stars would either be starved at the same time and preference tested the same day, or they would be tracked individually and share the same testing schedule as the others - i.e. they would all go x days being fed as normal, then starved for three days, then preference tested):

Consistency with testing like the measuring and weighing is key to good data. Record everything you can.

Two things: The biofilms offered need to be different but if the live rock is presumably from the same source how will it differ enough to make a difference since it's spreading onto the dead rock from the same live rock?
Also, I'm not sure I'm going to have access to a microscope high quality enough to positively identify the level of variation between the pieces of rock.

 

[livinlifeinBKK]

Also, I would love to identify the specific microorganisms being consumed but since I don't have access to some necessary equipment such as a powerful microscope maybe I should start out simpler. Part of the reason for the experiment is to enable reefers to be able to keep these stars in smaller tanks and your average hobbyist probably isn't going to have the time or resources to grow a specific type of biofilm for their star so maybe I should start out with something simpler before moving up the scientific ladder (after all this is going to be in my little apartment with just my resources available). Maybe starting out with something more basic and feasible for an average hobbyist who wanted to keep a star should come first. For example weighing and keeping track of growth of one star fed from biofilm that's been growing on dry rock but seeded by live rock from the ocean, one star fed with biofilm grown with the aid of a flocculant, and one star fed a diet of aquarium foods like Masstick and oysters only. That way if it was found that significant growth occured in one star or one star showed significant weight reduction, it would enable your average hobbyist to sustain a star themselves. Then I can continue the study and make it increasingly scientific and complex.

 

[ISpeakForTheSeas]

Two things: The biofilms offered need to be different but if the live rock is presumably from the same source how will it differ enough to make a difference since it's spreading onto the dead rock from the same live rock?
Also, I'm not sure I'm going to have access to a microscope high quality enough to positively identify the level of variation between the pieces of rock.

It might differ enough, it might not - that's why the microscope observation confirmation would be important. I would assume there will be at least some variation between individual pieces of live rock regardless of source, but to know if there is enough or not would require a microscope.

If you don't have access to a strong enough microscope, you would essentially either need to just assume there are differences and proceed as planned, pick just one live rock to use for growing out feed from (which would, presumably provide a more consistent biofilm than using multiple live rocks which may or not have differences) and proceed from experiment two on, or accept that it might take a while for your biofilm composition to turn out consistent (as it would take time for the microbes to determine a pecking order, so to speak - how long this would take, if it ever does sort out, is anyone's guess) and just assume that all the biofilm is the same value-wise from the stars' perspectives (this would not be preferred).

 

[ISpeakForTheSeas]

Also, I would love to identify the specific microorganisms being consumed but since I don't have access to some necessary equipment such as a powerful microscope maybe I should start out simpler. Part of the reason for the experiment is to enable reefers to be able to keep these stars in smaller tanks and your average hobbyist probably isn't going to have the time or resources to grow a specific type of biofilm for their star so maybe I should start out with something simpler before moving up the scientific ladder (after all this is going to be in my little apartment with just my resources available). Maybe starting out with something more basic and feasible for an average hobbyist who wanted to keep a star should come first. For example weighing and keeping track of growth of one star fed from biofilm that's been growing on dry rock but seeded by live rock from the ocean, one star fed with biofilm grown with the aid of a flocculant, and one star fed a diet of aquarium foods like Masstick and oysters only. That way if it was found that significant growth occured in one star or one star showed significant weight reduction, it would enable your average hobbyist to sustain a star themselves. Then I can continue the study and make it increasingly scientific and complex.

That's fair. Honestly, the purpose of identifying the specific type/composition of the biofilm would be to enable commercial reproduction, not hobbyist reproduction, as I agree that it would be well above the resources and time commitment of most hobbyists (I actually have been looking into this, and it would be extremely labor intensive - at least to start - and prohibitively expensive). Either way, as I mentioned in an earlier post, neither this suggested study nor a simpler study would necessarily tell us how to keep a star successfully long term - whether or not they would enable us to do so would only be known if the stars live a long time (such as their natural lifespan or longer) on the diet.

That said, a simpler study with foods regularly available to the hobby would also be a good place to start, and while the long term effect won't be known for some time, it could still provide some valuable insight regardless.

 

[livinlifeinBKK]

That's fair. Honestly, the purpose of identifying the specific type/composition of the biofilm would be to enable commercial reproduction, not hobbyist reproduction, as I agree that it would be well above the resources and time commitment of most hobbyists (I actually have been looking into this, and it would be extremely labor intensive - at least to start - and prohibitively expensive). Either way, as I mentioned in an earlier post, neither this suggested study nor a simpler study would necessarily tell us how to keep a star successfully long term - whether or not they would enable us to do so would only be known if the stars live a long time (such as their natural lifespan or longer) on the diet.

That said, a simpler study with foods regularly available to the hobby would also be a good place to start, and while the long term effect won't be known for some time, it could still provide some valuable insight regardless.

Don't get me wrong, I would love to do a full investigation into their natural diet...I even asked one of my university professors if I could carry it out at the school but unfortunately he said the university makes it really difficult to get permission to carry out studies with live animals

 

[ISpeakForTheSeas]

Don't get me wrong, I would love to do a full investigation into their natural diet...I even asked one of my university professors if I could carry it out at the school but unfortunately he said the university makes it really difficult to get permission to carry out studies with live animals

Yeah, to get university approval to work with live animals is a difficult process in the states too (lots of ethics rules and regulations).

 

[livinlifeinBKK]

Yeah, to get university approval to work with live animals is a difficult process in the states too (lots of ethics rules and regulations).

So with that in mind, what foods would you choose to test with? I'm definitely getting some of that live rock the shop near me just got in stock and maybe I'll rescape my 20 gallon with it since it's full of aiptasia now anyway.

 

[ISpeakForTheSeas]

Well, you've already found they eat oysters and Masstick, so those would probably be good things to start with. Beyond that, I'd probably pick a frozen omnivore food and/or a pelletized omnivore food (preferably commonly available ones) and go from there. Additionally, you could still pick a nice piece of rock and use it as biofilm culture starter (either to use the biofilm as one of the food options for the simpler study, or to use it to do the second experiment I listed above and proceed from there).

 

[livinlifeinBKK]

Well, you've already found they eat oysters and Masstick, so those would probably be good things to start with. Beyond that, I'd probably pick a frozen omnivore food and/or a pelletized omnivore food (preferably commonly available ones) and go from there. Additionally, you could still pick a nice piece of rock and use it as biofilm culture starter (either to use the biofilm as one of the food options for the simpler study, or to use it to do the second experiment I listed above and proceed from there).

Well since I'll probably be getting several pieces of that nice live rock I'll make use of it too. Maybe even put a piece of the live rock in one of the tanks every week and rotate different pieces in and out to see the growth difference when fed a diet as close to natural as possible vs the Masstick vs. oysters, vs an omnivore food...you saw that rock I posted, right? It was probably just in the ocean a few days ago.

 

[ISpeakForTheSeas]

Well since I'll probably be getting several pieces of that nice live rock I'll make use of it too. Maybe even put a piece of the live rock in one of the tanks every week and rotate different pieces in and out to see the growth difference when fed a diet as close to natural as possible vs the Masstick vs. oysters, vs an omnivore food...you saw that rock I posted, right? It was probably just in the ocean a few days ago.

I did - it's beautiful rock. I think that would be a good idea. Again, personally, I would toss a couple of pieces of dry rock in with each piece of live rock you put on its own so that you can have "backup copies" of each potential biofilm (so when you put one into the tank, you don't lose that potentially unique biofilm altogether), but it's definitely not necessary for a simpler experiment like this one.

 

[livinlifeinBKK]

I did - it's beautiful rock. I think that would be a good idea. Again, personally, I would toss a couple of pieces of dry rock in with each piece of live rock you put on its own so that you can have "backup copies" of each potential biofilm (so when you put one into the tank, you don't lose that potentially unique biofilm altogether), but it's definitely not necessary for a simpler experiment like this one.

That's a great idea!

 

[livinlifeinBKK]

And honestly thinking about Masstick, it might turn out to be a good food for starfish being an easily digestible paste that's made from natural plankton and other ingredients. He's definitely drawn to it!

 

[Dan_P]

And honestly thinking about Masstick, it might turn out to be a good food for starfish being an easily digestible paste that's made from natural plankton and other ingredients. He's definitely drawn to it!

Greetings! Sorry about showing up late. Very aggravating. I read the thread. Tons of good ideas. I will try not to be redundant.

Pilot Studies
I feel strongly about understanding the animal before experimenting on it. I would maintain several sea stars for some months, learning about what is normal behavior and feeding rate. During this pilot study, I would practice the weighing procedure. I would make sure the sea star identification method works. If my sea stars do not gain weight during this period, I would extend the pilot study until I know how to grow them.

Replication
The study you propose is sound with the caveats of advisors on this thread. It is still complicated and I wonder whether it is adequately controlled. Replication is going to be very important. The pilot study is going to give you an idea how variable weight gain is and in turn, this will give you an idea how many sea stars will be needed for each treatment, i.e., food type, to get statistically significant results. Biology data is just noisy.

Biofilm Food
You may find this to be the biggest headache in this study. You may find that it is a study in itself. Reproducibly supplying the same biofilm to the sea star will be a challenge. I think of the biofilm as another living organism, except it is invisible and I have no knowledge how to take care of it, let alone know what kind it is, how much there is of it and how much is consumed by the sea stare. All of this is critical knowledge in a nutrition study.

Advice Is Future Criticism
When you run your experiments, report the results and provisional conclusions, I would not be surprised to read critiques of your experiment that mirror the advice you are receiving. All this advice is coming back as criticism

I think you need to just take a first step with the knowledge that you will likely be restarting the experiment over many times. Tough questions are not easy to answer.

Looking forwards to your first report.

Dan

 

[livinlifeinBKK]

Greetings! Sorry about showing up late. Very aggravating. I read the thread. Tons of good ideas. I will try not to be redundant.

Pilot Studies
I feel strongly about understanding the animal before experimenting on it. I would maintain several sea stars for some months, learning about what is normal behavior and feeding rate. During this pilot study, I would practice the weighing procedure. I would make sure the sea star identification method works. If my sea stars do not gain weight during this period, I would extend the pilot study until I know how to grow them.

Replication
The study you propose is sound with the caveats of advisors on this thread. It is still complicated and I wonder whether it is adequately controlled. Replication is going to be very important. The pilot study is going to give you an idea how variable weight gain is and in turn, this will give you an idea how many sea stars will be needed for each treatment, i.e., food type, to get statistically significant results. Biology data is just noisy.

Biofilm Food
You may find this to be the biggest headache in this study. You may find that it is a study in itself. Reproducibly supplying the same biofilm to the sea star will be a challenge. I think of the biofilm as another living organism, except it is invisible and I have no knowledge how to take care of it, let alone know what kind it is, how much there is of it and how much is consumed by the sea stare. All of this is critical knowledge in a nutrition study.

Advice Is Future Criticism
When you run your experiments, report the results and provisional conclusions, I would not be surprised to read critiques of your experiment that mirror the advice you are receiving. All this advice is coming back as criticism

I think you need to just take a first step with the knowledge that you will likely be restarting the experiment over many times. Tough questions are not easy to answer.

Looking forwards to your first report.

Dan

I'm currently gathering all the materials I need for the experiment so it's a long road ahead but one I'm excited about! I feel the close observations I've made over the previous 6 months with the star I already have has been a start to the learning experience itself...who would've known a Fromia would be attracted to and eat oysters and Masstick before for one thing? I look forward to making future discoveries!