I have a 125 gallon tank; temp is 78-80 degrees Fahrenheit; ammonia and nitrites are 0 and nitrates are around 10. The substrate is gravel; I have been unable to afford a good light for this tank (they are expensive!) to be able to put in good plants, but I am saving up the money for that as well. The fish in it are ONLY mollies.

Lately, many of my "tweens" (between fry age and bearing age) have been falling ill to a mysterious disease. They sometimes get skinny first, but most of the time they do not. Then they start whirling and get a crooked spine. At that point, I have to euthanize them because it is inhumane to watch it.

The weird part about this mystery illness is that it will hit the fish in a matter of hours. One minute the molly is swimming around happily eating/pooping/playing, and the next minute he or she is whirling with the crooked spine. It's become very heartbreaking to watch. Another weird thing about this mystery illness is that it only affects "tweens"; my adult fish are not bothered by it at all.

I have treated the tank with antibiotics thinking there was some sort of internal bacterial infection because one of the fish developed pop eye (none of the others did). That did not stop this. I started adding more salt with the water changes. That has not stopped the whirling. I have tried formaline in case this is a parasitic infection; no change. On a daily basis, I am pulling out dead or almost dead fish from this tank.

A few possible scenarios have crossed my mind: Livebearers are prone to inbreeding. Could this be some sort of inbred birth defect?

Another possible scenario that I thought about was this: several months ago I treated the tank for calanus worms and everyone healed up fine; there are no more worms. I treated with Levamisole (recommended for treating these worms) that I got from our local feed and seed store. I measured it down precisely with a milligram scale and dosed the tank accordingly. These current "tweens" may or may not have been fry at that time. It is hard to keep track because some of the current "tweens" were in the fry tank which I also treated for the worms as I was quarantining them at the same time of the worms outbreak. Could that have affected them severely? Could the levamisole affected any pregnant females that were carrying fry so that the fry could have birth defects?

A final scenario is that I just have not yet found the right combination of medications to give to the tank. I used doxycycline because the water here is very hard (i.e. high in natural calcium) and because tetracycline does not do as well in harder water then the derivative, doxycycline, is used in its place.

Any help or thoughts or suggestions would be greatly appreciated! I love these mollies like they were part of my family, and they are! I have included my e-mail address. Please feel free to email (please no spam) or reply to the post if you can think of anything. Thank you!

jennifer.rutt@gmail.com

Are the adults all from the same family? Although, I have inbred fish to create weird looking Endlers I have never done this with mollies. I think the doxycycline had adverse affects on the developing fish ; it can cause defects on the bone. Try breeding some of your mollies with some molliesfrom completely different ones from another tank.

Jennifer,how many water changes do you make a week and do you use a gravel tube?How many and what kinds of filters are on you tank ?How many fish are in your tank?What kind of fish food do you feed your fish?Do you feed live food and what kind?When you change water do you use a water conditioner.Sorry for all the questions but what you are describing can be caused by a few things.You definitely have a bacteria problem and you may have a deficiency problem.

interesting.
yea, vitamin C deficiency could do the bent spine thing. old foods lose their vitamin C.
It happens in koi from lightning strikes. maybe stray voltage?
TB should be slower than that.

Sorry about your fish :( I was just thinking that maybe the calcium remover removed too much calcium? I live in an area of extramy hard water also, and have never had any problem with my mollies. (edit) do you use the calcium remover with every water change? Do you notice the fish dying more after you change the water?

Betty I think your are on the right road,a deficiency of some kind.I was thinking of vitamin D.proper lighting can prevent D deficency ,the active rays affect ergosterol in the skin of the fish and change it to the irradiated form which is vitamin D.Sometimes whole aquariums will show bent spines but generally only a few of the fishes are affected.There is no treatment,it is a matter of prevention.

Perhaps... tho they are getting some light. and they should be getting vitamin D in their food. I don't think it's as bad as vitamin C about degrading over time. tho it's an oil and could go rancid I guess.

So how much of what kind of light is the tank getting?

Here's some info on levamisole
http://www.drugs.com/mmx/levamisole-hydrochloride.html
Quote:

rapidly growing tissues are more succeptible to being messed with, so younguns would be more succeptible. However, I'd think those effects wouldn't have such delayed and then sudden onset. Seems like if the levi was going to mess with their genetics, it would have happened soon after it was dosed.

Does the twirling seem related to the bent spine to you?

I had had horrible luck keep mollies alive. I quit keeping them for that reason. Nothing seemed to work. Mine had spitting, emaciation, lack of coordination, shimmying and dead. no bent that I can find mentioned. I tried jungle parasite clear and it didn't touch whatever was going on.

I have a moderator who's a vet student who might be interested in doing necropsy/pathology to see what's going on. I can ask her if you want.

I don't think the doxycycline was a good idea. It can cause birth defects in humans the same way it does in fish; it causes defects in the bone and teeth.

I agree with you Alex,medication is not always the answer.But I find most people reach for it too often, looking for a quick fix.I'm guilty of doing just that. I stated raising a strain of molly(Cremecicle). Some of the young developed small red spots all over their bodies.The parents don't have any of these spots.Right away I reached for the Prazipro and Anchors Away and started a full treatment.But the spots were still there.So I called a friend of mine who raises mollys and he told me ,they come that way.
I think Jennifer's problems have more to do with nutrition then with birth defects.A lot of people put a lot of faith in dry foods.Unfortunately most of these companies are more interested in their bottom line then quality fish foods.

Here are some gel food recipes that all my fish eat as their staple diet. I don't feed dry commercial foods at all except for an occasional algae wafer for the snails and plecos (IMO algae flavored multigrain cheerios!) and haven't in a couple of years.
http://thegab.org/Articles/GelFoodRecipes.html
Might be good to whip up a batch with added vitamin C.

Also, here is a recipe that uses babyfood
http://thegab.org/forum/viewtopic.php?t=17481

I'll bet they'd also like eating an orange slice, kiwi, etc if you floated it in the tank.

The best commercial food IMO is made by mazuri. Unlike other commercial foods, you know it's fresh because you're buying it from the manufacturer and it isn't loaded with less digestable heat treated grains found in other commercial foods (they use those for protein so they don't have to include as much of the more expensive fish meal, etc).
http://thegab.org/forum/viewtopic.php?t=7279&start=0

The almost natural foods look good as well
http://thegab.org/forum/viewtopic.php?t=11432&start=0