Fish turning up dead.

Question
Hi there Stephanie.

I have a 55 gallon freshwater tank and have had several fish turn up dead in the last week. I had 3 Angelfish (small, about 2-3 inches), 3 Redtail Sharks (2-3 inches), 2 Ruby Barb, 2 Green barb, 4 Red Serpae Tetra, 4 dwarf platys, 3 cory cats, 9 Rasboras.

I have had the water tested and everything is coming up normal. However in the last week I have lost 2 rasboras, 1 green barb and 2 of my Angels. There are no signs of stress or disfigurement on any fish and the shop I use, who usually are spot on with any information they give me, are at a loss.

I have 2 Emperor filters on the tank, 2 amazon swords and 2 red luagas. I do a 15% water change once a week or so, and change the filters media once a month. Filters were all cleaned last month. Tank is about 8 months old now.

The last fish to be added were 3 rasboras and 1 ruby, about 2 weeks ago now.

Any thoughts on what might be the problem?

Answer
Hello,

If many fish die with no signs of disease then it must be a water quality issue. There is really no other logical explanation. However, if the tests you had done on the water appear ok, then you'll need to start stretching your brain to think of what else could be causing water pollution that the tests would not notice. Here's some suggestions:

1) Did anything spill into the tank? Were any cleaners used near it?

2) Are you using the proper dosages of all necessary chemicals? One time my fish all died because I added too much dechlorinator. Double check all your labels and make sure you understand what they are saying. For example, water conditioners may say add 5 mL/ 10 gallons, but this is for every 10 gallons you ADD, not including what is already in your tank. Denitrifiers and products like them may say 5 mL/10 gallons that are in your tank. These are very different amounts and it was this mistake that killed my fish once.

3) What was the water tested for? Ammonia, nitrites, nitrates, chlorine and free iron are all things that can kill your fish.

4) Do any of your decorations appear to be eroding? Substances that dissolve in the water from decorations could pollute your water. Also, are all your decorations aquarium safe?

I hope one of these suggestions will help.

Regards,
Stephanie