We're getting ready to make a rack system finally for our 2 balls & 2 corns. I really like Adriana aka Argentra's simplified version using UTH's...so I think we're gonna use her very informative instructions for building one w/a few tweeks here & there. We will be using 18 x 26 x 15 polycarbonate tubs. They'll be identical almost to the ones Adriana uses, just not the sterilite sort of tubs. She used a 30-40gal UTH on the warm side and a 10-20gal UTH on the cool side. We're in Texas and our house is never really that cold, so we were thinking of not using a UTH on the cool side (they don't have one in their glass tanks now) My question is...can you use 2 10-20gal UTH's butted up to one another or should we spend the money on the quite pricey 30-40gal UTH's. I recently got a great deal on Craigslist for several 10-20gal UTH's for $5ea (yes, they were new). So I'd really like to use 2 of those each per tub if possible so i don't have to spend $35ea on new ones elsewhere.