Hi! Thank you so much for your reply! I don't know for sure what the illness was. One of the Celebes casualties had some tiny white dots on it before it died so I suspected ich. And you know what, now that I'm thinking about it and trying to remember, the Boesemani might have showed some tiny white dots as well??? And he did dart around the tank crazily for a day or so before he started gasping and swimming at the top of the tank right into where the HOB filter empties water into the tank. I gave the tank one full dose of Ich-X as part of the quarantine trio, but when I decided to do the full Maracyn treatment, I suspended giving the Ich-X since it wanted water changes before every additional dose and the Maracyn wanted no water changes until the end. Maybe the Boesemani injured himself way back then (~3 weeks ago) and I only just noticed?
The Boesemani is definitely not being bullied, though. He's far and away the biggest fish in the pond. :) I bought 4 Boesemani rainbows and 4 turquoise rainbows back in January of 2014, and he's the only one left now. His tank mates are 4 Corydoras, 8 lyretail guppies, the 1 Celebes rainbow, and the most recent addition -- 1 nerite snail.
On the topic of tank mates.... I was debating whether I should try more Celebes rainbows? They are supposed to be best in groups, and I now only have the one survivor. I certainly don't want to kill any more of them, but now I wonder if I could have kept my initial batch alive if I had known to do the quarantine tank and med trio immediately? Would you try them again or avoid them?
Thanks again!!