I think Lucky is okay with that now because the young fish is bigger than I thought! I eyeballed a buce leaf against the glass that was the same length as the little catfish, and then used a ruler. He's one inch long now.
Um, yeah: I wrote this a few days ago and since have plugged current specs of my tank into AqAdvisor (online aquarium stocking calculator). The little sponge filter I had was previously ok for one betta and some snails, but with these catfishes it's definitely overloaded. I'm doubling the filter capacity- adding a second sponge- running on split airline- that's already seeded from the 38's canister. That keeps things just out of trouble for now, but it's still too many fish. If I move out the oto it would be better- if it was warmer I could put him back in the 20H with Perry, but then he'd get lonely... I could relinquish him to the pet store, but I hate to feel like I gave up on this one fish. Like I have a duty to it for life- and it can live a good ten years... but without its own kind now. Sigh.