This might be controversial:
Copperband butterfly! Just hear me out. Please.
Assuming you get one that is not beyond hope. (But this goes with most all specimens, coral or fish. Although I know that alot of copperbands can arrive at the LFS beyond hope.)
Copperbands get a bad rep for being hard to feed and eventual doom. But if you get one in semi-salvagable state, TRUST ME. BLACKWORMS.
I have experience with fattening up about 2 dozen Copperband butterflies (and other fish) in a span of 10 years helping the petland store acclimate poor arrivals in trade for free cat food. I felt like a volunteer in a dog/cat shelter. Lol!
They will squiggle around for at least 20 seconds while they drift down, and if the copperband notices it, he will be interested. He will peck at it. He will love it. They will still squiggle around when they land for a bit. I know copperbands aren't used to picking at food in the water column (but trust me, once your copperband is well established, he will be a master water column feeder...)
I have gotten Petland discounts store in my neighborhood (back in the day) to fatten up newly arrived Copperbands as well as other poorly shipped fish. For some reason, this branch sold live blackworms shipped from Cali for about 10 years before they shut down. But they never thought to feed their new salt water inhabitants blackworms. I made a suggestion and showed them what blackworms can do for struggling new arrivals.
Willie the Copperband in my youtube video is from that store! Luckily he was in decent condition and when I tried literally EVERY FOOD for him when I first got him, he was instantly gorging on blackworms.
The disposable plastic pipette is key in aiming blackworms in the copperbands direction, even if the fish is shy and scared and running away from everything, hiding in the corner.
TLDR:
1) Copperband butterfly fish are known to die due to inability to get nutrition. Get one that is at least swimming normally. Even a specimen with a concave belly has hope, as long as it is showing normal swimming behaviour.
2) Buy disposable pipettes. Get some live blackworms.
3) Spend 3 straight days concentrating on blowing live blackworms without scaring the poor fish in a QT tank. Blow above him so the blackworms slowly descend in its general direction, while they are squiggling madly along the way.
4) Using modified pavlovs conditioning, the copperband will also eventually eat frozen/freezedried tubifex and bloodworms (bloodworms are like candy). High probability is mysis shrimp. I have NEVER seen copperbands eat flake. If they get tricked into eating some from a mixed pipette of blackworms and flake, they will spit the flake food out.
Copperband + Blackworms = Success.
I promise you, after that. Copperbands are almost as hardy as damselfish as long as normal water parameters are OK and there were no parasites or disease.
