Vortex Diatom and Dead Fish

Question
I have a 55 gallon freshwater tank with 3 foil barbs, 2 balas, 2 goramis, 3 danios annd a pleco. LFG looked at tank and says it is not overloaded fish wise. I has been cloudy for about 3 months, even with regular 20% water changes and a couple of 50% changes.  Still reclouds after a few hours/days.  I have a Filstar with 3 trays.  Filstar pads, ceramic and carbon media. Good areation.  Sunday I installed a Vortex XL in place of the Filstar. After 3 diatom changes and 24 hours have sparkling water.  HOWEVER,this morning, Wednesday, I found both Balas and one small barb dead with bloody gills.  Other fish seem stressed and are "cruising" the top. Did 20% water change as it was all I had in the house.  Could Diatom filter be cause?  Could it be too good? What do I do from here to try and save the rest?

Answer
Hi Bob;

The diatom shouldn't cause it. I've used them for years with no problems like that. It takes long term use of several weeks for it to remove too much of anything from the water. Do another water change, vacuum the gravel and then have your tank water tested. Bloody gills often indicates ammonia poisoning or some other toxin. If ammonia is indeed elevated, make a 25% to 50% water change again and keep testing. Don't feed the fish right now while they are stressed. It will only add to the problem at this point so wait 2 or 3 days to offer anything. Fish are perfectly fine with no food for well over a week so it won't hurt them.

The cloudiness could be from overfeeding or overcleaning the filters. Overfeeding causes cloudiness by the accumulation of waste in the gravel. The beneficial bacteria that lives in the gravel and in the filter has not been able to keep up with it and has died from lack of oxygen in "dead spots" in the gravel. Poke at the gravel and see if there is any crud in there. If you stir up the gravel and gas bubbles rise from anywhere, expecially around the base of decorations, that can be even more serious. It means that hydrogen sulfide has developed in the gravel from anaerobic bacteria (bad bacteria) consuming the excess waste. The gas it makes poisons the fish. The extra filtration may have disturbed the gassy areas and released it into the water. To test this, take a few samples of the gravel where there is less circulation or crud and smell it. If it smells like rotten eggs then you know that's it.

If HS poisoning isn't the problem, could you be overcleaning the filter? Filter media should never be actually replaced unless it is literally falling apart or can't be rinsed enough for it to flow smoothly. Rinse it ocassionally, maybe every couple of weeks, but don't replace it. Too much cleaning kills the beneficial bacteria that consumes ammonia and nitrite from fish waste. Leave the filter alone to allow the bacteria colonies to stabilize. Filter manufacturers and fish stores want you to think otherwise. They make money from repeat sales of filter media. It just isn't necessary and can be very harmful to the system.

Here is a web page about toxins and their symptoms that may help you;

http://www3.sympatico.ca/drosera1/fish/illness.htm

There is a section on 'bacterial bloom' that may interest you too.

Let me know how things are going. I hope they feel better soon...

At Your Service;
Chris Robbins