For the past week I've lost a total of 3 goldfish. I feed them, their PH and temp is stable,they water is clear, the airater works fine, the filter is fine. Now, I've got a betta splenden in there, but he just nips the dorsal fins.
(one goldfish had a nipped tailfine too.) When I got it ( a guy gave it to me for free) I had to use Kaboom bowlcleaner and lime away to get it off without scratching the plastic. I rinsed it out good though. Is it possiple then when by betta nips the goldfish the chemicals that "somehow" stayed there are killing them?