whats the best way to heat tubs?

Im thinking about switching my two snakes to tubs, to make more room which will allow me to get more snakes. I was wondering what the best way to heat them are?

I use an undertank heating pad.

I use undertank heating pads as well, except I don't put them underneath my tubs. It seems like plastic resist heat much greater than glass does, so I put the pad inside the tub, and then just duct taped the cord to the back wall so that the snakes couldn't hurt themselves on it. And the humidity is AMAZING inside their tubs. You can do a number of things however, between heat tape, heating pads, etc. I just wouldn't suggest any kind of lamp with plastic, because they get WAY to hot.

IMO! A properly built rack with belly heat is the best to maintain the heat and create a gradiant from hot to cool side within the parameters. I've built a couple and found solid bottoms and tops with flex watt taped to the top of the bottom support piece works the best. The open racks using a 2 X 2 frame allow to much air to flow across the heating element causing a much larger swing in temps according to the Herpstat pro I prefer using on my racks. With solid bottoms and tops I seem to be able to maintain hot side to within 1 degree. With the open I see a 3 - 4 degree swing on the Herpstat pro. Also on my larger tubs, sweater box and up, I like to use the 11" flex watt. I have one rack that uses two strips of 4" and it just doesn't seem to work right. On shoe boxes I use 1 strip of 4" and it does a good job on them.

FlexWatt or Ultratherm's. FLexWatt is considerably cheaper but it made the same way. I use them on some of my tubs and the others are in a rack with heat cabling (zoo med) which works real well also.