Bowser is in the 2-3 gallon Kritter Keeper, I can never be sure of the gallon size. It's the medium one though. Ludey is in a 3 gallon. I don't know the brand of his tank bc I traded my 1 gallon with someone for it, but for a month or so Ludendorff was only okay with it half filled. I filled it last night and he's okay now :0 I think the space freaked him out all at once coming from the store.
Right now my boys are in the 1.75 petco keepers. I have two 10 gallons that will be set up for Cosmo and a future resident yet to be found. Looking for a darker with some red finnage King Crowntail. I had Mystic in the 10 gallon tank, but even when the water was pristine he seemed stressed by the filter and it's only 85GPH. He would just sit under his cave most of the day and would only come out for 30min or so at a time. When I turned off the filter he would come out and explore. As soon as I get my 10 gallons cycled and holders moved I'll upgrade him to an unfiltered 2.5 gallon aquarium on my desk. That's the largest I'm going to be willing to do a 100% change on for the guy.