Beviking...where I'm putting the tank is in the interior corner of an addition we added to the house about 10 years ago. One wall is right over the main floor support beam which has posts underneath it. I'm not so much worried about that one, I'll put the bigger tank on that wall. the wall i'll put the 55 on is where the addition attaches to the house. The floor joists run horizontal to this wall, so the tank would be sitting on the one joist. I guess I need to go in the basement with a flashlight and look. The contactor was a twit. WHen you step into this room the floor bounces here. The 10 gal I have now in this location wiggles when you walk near it.
As to the size of the tank, Holly..these 2 walls are in about a 5' L in either direction, so I need to get something that will "fit" and not obstruct a doorway. I'm better off having a wider tank that a longer or taller, so what I'm looking at is 48 long..and then go from there. Much taller tho and it will be harder to clean.
And I've been out on Ebay looking. There is a 70-or 75 not far from me, not sure if that is big enough for the clown loaches. I would like to get more. There is an even larger one I'd love to have..oh yes I do love my Ebay! I've gotten plants there...clothes, musical instruments, boxer dog collectables...my husband even found a picure of his great grandfather in civil war uniform.