75 gal and floor weight

Well my hubby is a truss designer/engineer so he would know the answer to this question.. I think that his answer is that it will be fine.. But I will ask him tomorrow just to be sure.

How old is the house? Is there any rotted wood or warped boards?

I think it should hold. If you are worried about in you could put something that weighs as much as the tank where you want to put it, like concrete bags, bunch of weights and dumb bells, etc. Wood is stronger than most people think. Also you could buy a bunch of 20 or 40 gallon tubs and fill them with water in the are, that way they would have a use for when you are done. I know I use a lot of those tubs for storage.

Since you're planning to place it against a load-bearing wall and perpendicular to the joists, the tank will probably be fine, but if you've any concerns at all, why not hire an engineer to come out and take a look? It will give you peace of mind - and if he DOES discover a potential problem, he will also be able to suggest effective ways to shore up the flooring.

Most standard residential building codes call for a 55 psf (pound per square foot) total load and atleast an L/360 deflection ratio for the design of floor systems now days. From the information I read here it looks like your room is a 12X20, and the wall your setting the tank against is load bearing so I'm assuming there is a girder and piers below that wall to absorb that load. A 2X10 Souther Yellow Pine #2 grade (1-1/2" X 9-1/4" actual dim.) joist at 16" on center is not recomended to span over 14'-8" at the standard loads I mentioned earlier. Assuming your tank is about 24"X48" at the base, your looking at about 100 psf... nearly twice the allowable load, but only in a small area. I doubt it would cause any severe structural problems but, you may notice a difference in deflection and vibration in that area. You could notice the tank rocking a bit when you walked through the room, and other minor vibration annoyances along with it. I would recomend adding a "stong back" about mid-span in that room perpendicular to the joists or along the outside edge of where the tank sits. it wouldn't take much really, a double 2X6 would work fine, with piers about every 8'. Just jack it up with a small hydralic jack until it's snug under the joists, if there are any that are crowned and aren't in contact with the strongback you can use regular door shims to close the gaps. This will reduce the vibration in that room but not actually act as a load bearing girder.

I hope this helps.

it should probably be good.

my 55g is upstairs and we have no problems with it.