Black Molly Quarantine

Humblefish

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** This information was originally posted here: https://humble.fish/community/index.php?threads/black-molly-quarantine.55/ **

Preface - Freshwater (FW) black mollies have been used for years in saltwater aquariums for algae control. However, this write-up will focus on their potential for identifying marine fish diseases present in a display tank (DT) and also quarantine tank (QT). The most important detail is to ensure you are using Freshwater black mollies for this purpose. Two reasons:
  1. Evidence of ectoparasites (e.g. ich, velvet, brook) will show as white spots on a fish or translucent for flukes. This makes them easier to see on a black colored fish.
  2. A freshwater black molly will have no acquired immunity to marine diseases, thus making it probable for visible symptoms to show. (In this study, a stable infection of Cryptocaryon irritans was maintained for 2 years using black mollies.)
Molly.jpg
Molly 2.jpg
Molly 3.gif


Acclimation - A slow acclimation period is best. I prefer to setup a simple 10 gal tank (pic below) and convert them to saltwater over a week. Most (freshwater) diseases the mollies were carrying will be eradicated once they are in full seawater. If you happen to see white stringy poo coming out of any of them, food soak API General Cure or Fenbendazole as outlined here. Mollies are primarily herbivores, prefer low flow and have other requirements explained here: Keeping, Breeding, and Raising Saltwater Mollies

The larger black mollies (Sailfin or Balloon) hold up better than the smaller ones in a saltwater environment.


Testing a Fallow DT - The only reliable way to eliminate a fish disease from a reef tank is to starve it out by going fallow: Fallow periods: Going Fishless

You can test to see if a fallow period has been successful by using 2-3 black mollies before introducing your QTd fish back into the aquarium. I advise a 2 week test period before giving the all-clear. You can house the mollies in an acclimation box or low flow area of your sump; or let them swim freely in your DT (they are easy to catch). If evidence of disease presents itself on any one of the mollies, they all need to be removed, treated and the fallow period restarts. Furthermore, these same mollies may no longer be suitable for testing marine diseases in the future. They are now SW fish who have encountered (and possibly started to build up immunity to) a marine disease.

QT Usage - Certain fish (e.g. anthias, mandarins, wrasses) are notoriously sensitive to medications such as copper and Prazipro. This can make it difficult to chemoprophylactically treat them for Ich, velvet, flukes, etc. Compounding the problem is wrasses, clownfish, dragonets and other species have a thick mucous coat which often hides visible physical evidence (i.e. white dots) of parasites. What to do? Black mollies to the rescue! :D

By quarantining black mollies alongside, this allows you to use them as "canary fish" to detect the presence of disease even if none of the other fish in QT are showing symptoms. This can be done via observation in a medication-free environment. However, I stress the following:
  1. The observation period does not start until mollies are added to the QT. This should happen as soon as (or even just before) fish are added. Because you are having to wait for any parasites to drop off, encyst and then release free swimmers to infect the mollies observation time should be 4-6 weeks.
  2. Be aware that not all SW fish are suitable tank mates for mollies. They are easily bullied or even eaten by large aggressive species (e.g. triggers, groupers, eels). So, the mollies may need to be housed in an acclimation box or by using a tank divider.
  3. Watch the mollies (and all the other fish) for symptoms of disease every single day. So, this is not a reliable method for those with busy schedules, or who will have to leave the QT unobserved due to work/vacation. Watch for visible physical symptoms to manifest (e.g. white dots/splotches), and also behavioral symptoms of disease. Heavy breathing, lack of appetite, scratching, lethargy, head twitching, swimming into the flow of a powerhead are all things which can forewarn you that trouble is on the way. :eek:
  4. Once symptoms of disease have been observed/detected, all fish in the QT must be treated ASAP. This includes the mollies! And again, any mollies who have encountered a SW pathogen should no longer be considered viable for testing marine diseases in the future.
  5. This method is less reliable for detecting flukes, since those often infect the gills and are more difficult to see when they crawl over the scales. (And they would crawl pretty fast over a small molly.) Still, a molly (dead or alive) can be checked for flukes at any time by performing a FW dip. This is going to sound harsh, but better to FW dip a hardy molly than subject a more delicate specimen to the same test.
Concerns - I understand some will have ethical concerns about using mollies as "canary fish", and I am sensitive to that. The more I research & experiment, the more I find there is no perfect solution when it comes to quarantining our prized specimens. However, using FW black mollies to test for SW diseases is an accepted practice by Marine Biologists and public aquarium curators. And I feel the science is solid to extend this practice to also include QT environments, for those hobbyists who prefer to just observe and/or less inclined to use meds as a prophylaxis. At the end of the day, the objective of QT is to introduce disease-free fish into the DT by any means possible.

However, I stress that once you buy FW black mollies you have a moral obligation to care for them the same as any other fish. They are not "throwaway fish" to be discarded after they have served a purpose. Mollies are "reef safe" algae eaters and adapt well to a reef environment. Or they can be housed in a quiet sump area (e.g. refugium) or as semi-permanent QT inhabitants (until a disease pops up.) You also have the option of just converting them back to full freshwater. However, I urge you to care for them yourself, or rehome them to someone with a dedicated FW tank. Sending them back to a LFS leaves open the possibility that another reefer may purchase them for the same reason, and those mollies might fail to test positive for a disease which they have already been exposed to.
 
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4FordFamily

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Fantastic article, now we need something about H202!
 

puffy127

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So if you use them in an observation QT and no disease pops up, can they stay there and be used for the next batch of fish that comes through the observation QT?
 
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Humblefish

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So if you use them in an observation QT and no disease pops up, can they stay there and be used for the next batch of fish that comes through the observation QT?
Yes; the only time black mollies need to be replaced is when they pop positive for a disease. Because their immune system has now been exposed to a marine pathogen and may now have acquired immunity.
 
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neilp2006

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This is interesting.

Can you use a black mollie as a canary in a coral or invert QT? Add the mollie on the same day as an incoming batch of coral or snails, wait two weeks- move to DT if mollie is ok? Then repeat for a new batch?

If that’s possible, Way more palatable than 76 days.

Thanks!
 
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Can you use a black mollie as a canary in a coral or invert QT? Add the mollie on the same day as an incoming batch of coral or snails, wait two weeks- move to DT if mollie is ok? Then repeat for a new batch?
Yes; but if the molly hits for a disease you have a moral obligation to treat it and the fallow period in the coral QT doesn't begin until the molly is removed. Treating the molly can just entail quickly converting it back to freshwater and giving it to someone you know will never try to convert it back to SW. Because once a molly's immune system has been exposed to a SW pathogen, one must assume that immunity/resistance is possible.
 

neilp2006

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Yes; but if the molly hits for a disease you have a moral obligation to treat it and the fallow period in the coral QT doesn't begin until the molly is removed. Treating the molly can just entail quickly converting it back to freshwater and giving it to someone you know will never try to convert it back to SW. Because once a molly's immune system has been exposed to a SW pathogen, one must assume that immunity/resistance is possible.
Awesome- yes, if I go this route, I’ll be doing it ethically and treating and hiking any diseased mollies
Thanks so much!
 

NYBumkin

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Maybe this is covered somewhere else...but what if I want to just add a school of Mollies to my display tank and not use them as a method of disease detection? Would a quarantine process as you outline in your "how to quarantine" post be what should happen for the Molly's? With the addition of a week of fresh to salt water acclimation beforehand?

Thank you!

Performing my first "Humblefish Quarantine" on our first fish for our soon to be first reef tank!

IMG_9196.JPG
 

neilp2006

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Maybe this is covered somewhere else...but what if I want to just add a school of Mollies to my display tank and not use them as a method of disease detection? Would a quarantine process as you outline in your "how to quarantine" post be what should happen for the Molly's? With the addition of a week of fresh to salt water acclimation beforehand?

Thank you!

Performing my first "Humblefish Quarantine" on our first fish for our soon to be first reef tank!

IMG_9196.JPG
NOpe!!

Since they would have no marine parasites present, a 7-12 day salinity ramp from freshwater to 1.026 iscall that's required. They will be completely naive of marine parasites, and, as a bonus- clear of freshwater parasites too since they are now in hypersalinity conditions compared to freshwater.

While you are doing the salinity ramp- if you notice stringy poop etc indicating internal intestinal parasites, I think you can treat them as you would for a marine fish- general cure soaked food for 10 days (although if they are eating flakes, not sure how easily that would go)

What I did was take the tank volume (8 gallons) divided by 16 days - so half a gallon a day. IF you remove 1/2 gallon from the tank and replace it with 1/2 gallon of 1.025 every day, in 16 days it'll be at 1.025 (actually 13.5 days or so due to reasons). To make sure that was s safe rate- I calculated the delta between 1.025 - 1.000 = 0.025 then divided it by 16 days to get salinity rise per day = 0.0015sg/day. Maybe a touch higher than the typical 0.001 sg/day but who really counts that third decimal place?

It worked very well. I transferred them to my 20 long at 1.026 after starting the salinity ramp on 3/2. All survived, expiring and eating great. One might even be pregnant, lol
 
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NYBumkin

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NOpe!!

Since they would have no marine parasites present, a 7-12 day salinity ramp from freshwater to 1.026 iscall that's required. They will be completely naive of marine parasites, and, as a bonus- clear of freshwater parasites too since they are now in hypersalinity conditions compared to freshwater.

While you are doing the salinity ramp- if you notice stringy poop etc indicating internal intestinal parasites, I think you can treat them as you would for a marine fish- general cure soaked food for 10 days (although if they are eating flakes, not sure how easily that would go)

What I did was take the tank volume (8 gallons) divided by 16 days - so half a gallon a day. IF you remove 1/2 gallon from the tank and replace it with 1/2 gallon of 1.025 every day, in 16 days it'll be at 1.025 (actually 13.5 days or so due to reasons). To make sure that was s safe rate- I calculated the delta between 1.025 - 1.000 = 0.025 then divided it by 16 days to get salinity rise per day = 0.0015sg/day. Maybe a touch higher than the typical 0.001 sg/day but who really counts that third decimal place?

It worked very well. I transferred them to my 20 long at 1.026 after starting the salinity ramp on 3/2. All survived, expiring and eating great. One might even be pregnant, lol
Nice! Thank you!!
 

AcroNem

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Maybe this is covered somewhere else...but what if I want to just add a school of Mollies to my display tank and not use them as a method of disease detection? Would a quarantine process as you outline in your "how to quarantine" post be what should happen for the Molly's? With the addition of a week of fresh to salt water acclimation beforehand?

Thank you!

Performing my first "Humblefish Quarantine" on our first fish for our soon to be first reef tank!

IMG_9196.JPG
NOpe!!

Since they would have no marine parasites present, a 7-12 day salinity ramp from freshwater to 1.026 iscall that's required. They will be completely naive of marine parasites, and, as a bonus- clear of freshwater parasites too since they are now in hypersalinity conditions compared to freshwater.

While you are doing the salinity ramp- if you notice stringy poop etc indicating internal intestinal parasites, I think you can treat them as you would for a marine fish- general cure soaked food for 10 days (although if they are eating flakes, not sure how easily that would go)

What I did was take the tank volume (8 gallons) divided by 16 days - so half a gallon a day. IF you remove 1/2 gallon from the tank and replace it with 1/2 gallon of 1.025 every day, in 16 days it'll be at 1.025 (actually 13.5 days or so due to reasons). To make sure that was s safe rate- I calculated the delta between 1.025 - 1.000 = 0.025 then divided it by 16 days to get salinity rise per day = 0.0015sg/day. Maybe a touch higher than the typical 0.001 sg/day but who really counts that third decimal place?

It worked very well. I transferred them to my 20 long at 1.026 after starting the salinity ramp on 3/2. All survived, expiring and eating great. One might even be pregnant, lol
@Humblefish I have not read studies into this, as it isn't a practice we used in quarantine and I have never done this in personal systems either. So please correct me if I'm wrong.
But I believe this could only be done with the assumption that everything else in the system has been properly quarantined and treated for other parasites, as the addition of a freshly exposed fish into an established system would simply allow Cryptocaryon (or whatever parasite is potentially in the system) an open path to freely reproduce. Is this accurate?

Edit* If the question was that you only wanted to add a school of Molly's to a fallow system that is clean or are adding them first then adding fully treated animals after, then I understand that this is correct. But my other question still stands. Sorry for the long winded post.
 
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Humblefish

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@Humblefish I have not read studies into this, as it isn't a practice we used in quarantine and I have never done this in personal systems either. So please correct me if I'm wrong.
But I believe this could only be done with the assumption that everything else in the system has been properly quarantined and treated for other parasites, as the addition of a freshly exposed fish into an established system would simply allow Cryptocaryon (or whatever parasite is potentially in the system) an open path to freely reproduce. Is this accurate?

Edit* If the question was that you only wanted to add a school of Molly's to a fallow system that is clean or are adding them first then adding fully treated animals after, then I understand that this is correct. But my other question still stands. Sorry for the long winded post.
Freshwater mollies have no acquired immunity to saltwater pathogens. (You can't build up a resistance to something you've never been exposed to.) So, putting mollies in a tank where any marine disease is active will most likely (a) Kill the mollies (b) Provide a reservoir to fuel an outbreak for the rest of the fish. Mollies work as "canary fish" in QT only if you watch them everyday for symptoms of disease. If they "hit" the mollies should be treated along with the rest of the fish, and then either placed in your DT or converted back to FW. Once mollies have been exposed to a SW pathogen they are no longer suitable test fish because their immune system now has familiarity.

You can safely convert freshwater mollies to full SW without QT. The only thing I would treat for during the conversion process is soak their food with fenbendazole. They sometimes carry low-level cestodes (tapeworms) which survive even in saltwater.
 

neilp2006

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Freshwater mollies have no acquired immunity to saltwater pathogens. (You can't build up a resistance to something you've never been exposed to.) So, putting mollies in a tank where any marine disease is active will most likely (a) Kill the mollies (b) Provide a reservoir to fuel an outbreak for the rest of the fish. Mollies work as "canary fish" in QT only if you watch them everyday for symptoms of disease. If they "hit" the mollies should be treated along with the rest of the fish, and then either placed in your DT or converted back to FW. Once mollies have been exposed to a SW pathogen they are no longer suitable test fish because their immune system now has familiarity.

You can safely convert freshwater mollies to full SW without QT. The only thing I would treat for during the conversion process is soak their food with fenbendazole. They sometimes carry low-level cestodes (tapeworms) which survive even in saltwater.
Thanks Humblefish!

Like clockwork- I checked my mollies this morning fully acclimated at 1.026 for 3 days now- and 2/6 have white poop. Didn't see any the entire time they were acclimateing


I don't be have Fenbendazole, but I do have metroplex and focus. I've also get them eating TDO chromaboost pellets instead of flakes.

Should I try the met plus focus in the pellets? Thanks !
 
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Should I try the met plus focus in the pellets? Thanks !
Metro only treats internal flagellates, and your mollies are more likely to have intestinal worms (which prazi or fenbendazole treats).

I wouldn't food soak liquid Prazipro (explanation here), but API General Cure contains prazi + metro in powder form so that's your best option in lieu of fenbendazole.
 

neilp2006

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Metro only treats internal flagellates, and your mollies are more likely to have intestinal worms (which prazi or fenbendazole treats).

I wouldn't food soak liquid Prazipro (explanation here), but API General Cure contains prazi + metro in powder form so that's your best option in lieu of fenbendazole.
Perfect- I have a bunch of GC available

Thanks
 

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Freshwater mollies have no acquired immunity to saltwater pathogens. (You can't build up a resistance to something you've never been exposed to.) So, putting mollies in a tank where any marine disease is active will most likely (a) Kill the mollies (b) Provide a reservoir to fuel an outbreak for the rest of the fish. Mollies work as "canary fish" in QT only if you watch them everyday for symptoms of disease. If they "hit" the mollies should be treated along with the rest of the fish, and then either placed in your DT or converted back to FW. Once mollies have been exposed to a SW pathogen they are no longer suitable test fish because their immune system now has familiarity.

You can safely convert freshwater mollies to full SW without QT. The only thing I would treat for during the conversion process is soak their food with fenbendazole. They sometimes carry low-level cestodes (tapeworms) which survive even in saltwater.
Thank you for the final comment there about QT recommendations. That's what I was looking for! Could be a neat addition to a new tank for me. They eat algae right? :D
 

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