dojos/brown knife sickness

Question
I have had a wonderful brown knife and a couple of dojo's for at least 8 months now.  I have a 29 gal tank and we do a 2/3 water change weekly.  I feed them flakes and worms.  They were doing just fine, until about a week ago.  My knife got sluggish and looked like he was possibly shedding.  Within 24 hours his eyes were bright pink/red and he died.  Then my dojo's started acting the same way.. not so much on the scaly stuff but definately the pink eyes.  They died too.  I'm very sad and I'm afraid to introduce any new fish.  We've tested it for pH and it's 7.4 and there are no CO2's in the water.  I have not however tested it for NO2's.  The tank has been set up for 3 years.  I'm not sure about the NH3 levels either.  Do you have any idea what might be causing it and what can I do to make my tank a happy and healthy one again?
thanks so much,
Joleta

Answer
Hi Joleta;

Oh, how sad. I'm so sorry this has happened.

Often redness indicates a bacterial infection, but it could even be a toxin of some kind. Something simple like soap residue from your hands, lotion, nail polish, room freshener, disinfectant, etc., are all possibilities. It really is hard to say. If It was my tank I would start over. Drain the tank fully and rinse all the gravel and decorations in hot water. Throw away any carbon or zeolite (looks like white carbon) or foam filter pads and buy new ones.

A 2/3 water change all at once can be pretty stressful to your fish. Vacuum the gravel and change 25% of the water every week so the fish are more comfortable. Don't overfeed and there will be less waste to remove.

Remember that once you get it started it has to go through the break in period again. Here is a link to my article about it;

http://www.xanga.com/Expert_Fish_Help

At Your Service;
Chris Robbins