I have sadly suffered a total fish loss in my 4 month old system. My existing fish had seemed healthy and fine. I added some new fish, and apparently they brought a disease with them, because the entire system died off in a few days.
Some kind of brown spots were on the fish.Ammonia, nitrites, and nitrates are all at zero. PH is 6.8. I have four large airstones going in the tank, and while I don't have an O2 tester, if it was lack of oxygen for the increased number of fish, the problem should have corrected itself as the population dropped. I had just added some chelated iron. Though I had done that before and it didn't seem to cause issues.
Unless I missed something, my biggest question at this point is how long I should wait before adding new fish. I don't want to add fish to a diseased tank, and repeat the process. I imagine adding an antibiotic would undo all the good bacteria I have finally built up.
