Back in the saddle . . . and having problems!
I had aquariums for dozens of years, but it has been almost twenty years since my last one. In the past, I had a ten gallon with fancy guppies, plus a fry tank for them, a 15 gallon cold water tank with a goldfish or two, and a twenty gallon community tank with several species of tetra, corydoras, a loach…. that loach lived almost 9 years!
I got the bug again and decided to just have a 10 gallon tank and a goldfish or two, but then I ended up with three (someone needed to get rid of one) and so then I had to go get a bigger aquarium. Unfortunately, I'm having problems with the fish---trying to figure out what is wrong with them--my ammonia, nitrate, and nitrite levels are all zero and I have been diligent about water changes. But I lost one fish, a Shubunkin that didn't look ill until a few days before it died. I gave it salt baths for three or four straight days and it always perked up afterward but was worse the next day. Shortly after it died, the other two fish started flashing and "yawning" and now the larger one is on the bottom of the tank and gasping. What is wrong? Water quality is excellent. I've never had gill flukes in any fish in the past, is this what is causing this? If so, what is the best treatment?