hmm.. But not forever? If he was the sole fish in the tank? No plecos etc?
Hmm. I'm not ignoring you guys or anything. I'm going to buy a small 2inch EBJD. It will be the only in the tank, then maybe upgrade later. The only thing stopping me upgrading is the weight of the tank vs my bedroom floor lol. So a EBJD could happily thrive in a 3ft tank, but it would look a bit cramped?
Well no, I don't think a full-grown EBJD would be happy in a 3 ft tank. The weight of a full 55 US gal should be fine for a room on the second floor of a house.
These fish grow very slowly, so if you want to grow one out in the 42 that's fine, but if you don't plan to upgrade then maybe look at some fish that stay in the 6" range when full-grown.