Sudden deaths

Question
I have a lot of yoyos and clowns in a 50gal tank. I have a stone, 2 powerheads (one is pumping from UGF)pumping 2000LPH to a trickle filter, and a sponge filter. I have gravel in the tank and lot of plants. Water temperature is 30'C. I was not at home for a couple of weeks and when i came back I saw a lot of food spoilt and floating about. Food could be seen engulfed in strings of fungus or mould or i don't know what kind. I changed the water, But I find the yoyo's are not active as before. they seems to be not moving around much. Clowns are normal. I found 3 yoyo's have died in the tank. What kind of a medication can I put to cure them?

Answer
Hi Hasitha;

That's awful. So sorry this is happening to your fish.

Test the water for the presence of ammonia (NH3), nitrite (NO2)and nitrate (NO3). It will tell you how damaged the bio-system is. The beneficial bacteria that consumes the waste has become stressed too and much of it may have died during all the excess waste trauma. That means it can't control the toxins that the fish make anymore.

Unless you can see disease actually on them I don't think they need medication. Just keep gravel vacuuming and keep doing partial water changes. This will get the crud out of there and the toxins will go down and make them all feel better.

If you changed all the water and cleaned the gravel when you discovered the problem, that may be what is causing trouble now too. It's like starting a new tank full of fish. Testing the water will reveal if that's going on too. Or, it stressed the fish too much and they are still trying to recover. As you can see there are many possibilites. Test the water and get back to me as soon as you can...

At Your Service;
Chris Robbins