This Week I have had two mysterious deaths. One of my Juvenile Panda Cories died, and Just 30 minutes ago I pulled out a dead opaline Gourami.
This is a 20 gallon tank, and I must admit that I do have it overstocked. When I pulled out the panda, and the gourami, I checked the water quality.
I didn't bother Checking the Ammonia, because I have the SeaChem Ammonia Tester that suction cups to the inside of your tank, and that was showing as yellow as you can get.
When I pulled the Panda Cory out, which was a day after a 25% waterchange, my Nitrate Read at 0, and my Nitrate read at approximately 5ppm if memory serves me correctly. I just checked water parameters again when I pulled the Opaline Gourami, Ammonia Showed Yellow on the strip (0ppm), Nitrite at 0ppm, and Nitrate @ 10ppm.
Now My ammonia, nitrite, and nitrate in both instances were at acceptable levels, and should not have killed my fish. I do not see any tell tale signs of sickness in my tank. With the Exception of the opaline, over the past few weeks I've noticed that his colors would fade, and then he would brighten up. But this was sporatidic and I just associated it with mood swings.
Does anyone have any idears what is going on with my tank? Is there anything else I should be checking Chemically in a 20 Gallon Freshwater Tank, besides Ammonia, Nitrtite, and Nitrate?