I think I gave I gave almost 3 grand for my 85 gal. sub-mount installed. Can't be w/o it, but I wished it were a little more narrow. I'd actually be afraid to go with the 70 gallon ones I've seen, but I guess I could get used to it and make it work. I do like the way the 85 gal. model looks with the machine mounted on top of the tank, but it's very expensive for a water tank. I didn't think any other type of tank would work for me in my van. Still don't.