Upgrading tank soon, opinions please

Ok currently I have 3 axies, they are in a 20g tall tank with a canister filter, screen top, an aquarium fan, sand substrate, a hide that none of them use and bunches of plants to hide in. Their favorite place to be is in the tallest plant, they all sit at different levels of the plant. The axies are all about 5-6 inches, hatched last May. They're pretty lazy, I've got no athletes here lol. We moved into a considerably smaller place and although I'd planned on getting a 55g tank when I originally got my eggs, now that's not realistic for the space we have. I need to take some measurements but I'm not sure a 40 breeder would fit even. I started out with 7 eggs that hatched. I had only planned on keeping two, but only rehomed 4. So If I have to rehome another, I'm ok with that. But I really want to keep two of them. Would two (or even the three) be okay in a 20 long? I've seen that a single adult can do well in a 10g tank, but I don't really know if there is a #gallons per axie rule. I searched the forum for tank size but didn't get anything helpful. I really want to have a nice set up for them and have them be comfortable.

People will say 10 gallons per axie, but i don't think a full grown axolotl can live in a 10 gallon happily. I have one 5 inch axolotl in a 10 gallon and she definitely needs more room. My 20 gallon long has only one axolotl and he is VERY content. I also have a 29 gallon for my full grown axolotl and i don't think i would want another in there, either. I recently bought a 30 breeder and from the looks of it, i would feel comfortable putting three axolotls in it considering the amount of gallons but also how wide and long the tank is.
Hope this helps.

thank you, yes that does help! I think that we are probably going to keep two of them and shoot for the 40 gallon tank.