On May 3, 7:44 am, wrote:
you broke a cardinal rule. never add new fish to old tank without quarantine.

I don't understand the connection with what I wrote. How would a
quarantine have prevented the small fish from eating the fins of the
larger??

you need to check your water parameters. nitrates are probably way high.

Again, I'm missing the connection. Are you saying that high nitrates
stimulate fin eating??? That's amazing. But I'm probably
misunderstanding
you somewhere.