bloated fish then die

Question
We have a 20 gal. tank with mollies, guppies, and tetras. we have had the tannk set up for about 3 mos. but just recently some of the fish become bloated almost looking pregnant then turning almost like white or loose some of their colour then bellyup in the morning. What could be wrong?

Answer
Hi Cindy
My initial thought is it sounds like dropsy-basically where fluids build up inside the fish.  I've attached a link at the bottom, also has photos, just click on the "dropsy" in white, and it'll scroll down to the right area.

Dropsy is usually brought on by poor water conditions.  How often are you doing water changes?  These should be done once a week, about 25-30%, depending on how overstocked the tank is.  So, that's my next question, how many are in the tank-before and after fish deaths?  I'd recommend getting a water test kit, and testing your water for ammonia, nitrites, and nitrates.  The first 2 should read 0 ppm, and nitrates under 20 ppm.  Anything over those amounts is considered "poor water conditions" that stress the fish and bring on all kinds of problems for them.  

I would do an immediate water change, about 35-40%.  Pick up from the pet store, a bottle of medicated food.  I know PetSmart sells it, think it's made by Jungle Labs?  They have one that's an anti-biotic and one that's anti-parasitic.  You'll want the anti biotic one.  Not sure if that will help, dropsy is usually fatal for fish.  The foods are fairly new to the market.  It's a good way to get the antibiotics inside the fish, as opposed to dosing the water with it.  Hopefully the fish is still eating. A lot of times, just doing the water changes, and keeping the water parameters in check is enough for the fish to fight off the illness.  I've also heard of doing an epsom salt bath.  Epsom salts are known to help "draw out" fluids.  I'll have to search around for dosage instructions for that one.  Try the other suggestions first, if that doesn't help get back with me and I'll love for the Epsom salt info.  

http://www.fishpalace.org/Disease.html#Dropsy

Hope that helps!

Christy