Here's the ones I use:
1754 6/12 uses 2 15qt or 1 32 qt tub per level, at 180 with HEAT these are an awesome buy!
The 4 level Iris 900, are overkill but they do work for my monster gals & my SD Retic male (he's only 6 ft).
AP 10s are great for my SD & Madu gals.
You can get heat rope or request flexx-watt.