Is this acceptable for heat?

[demonicchild]

If you can keep your temps and humidity right, and your snake eating and shedding properly, then a 55 gallon will be fine. The issue is that it is difficult to keep heat and humidity right, and snakes will normally go off feed in such a large enclosure, because they do not feel secure.

If I were you, I would do your best to make sure your heat and humidity is the recommended range in the 55 gallon. If you are having trouble keeping these in the proper range, or you snake goes off feed, then move to a smaller tank.

Hope this helps.

But would the 20 be better until he is too large for it? I also have a very long, but short plastic tub. I really want to do what's best for my snake so I'm willing to do anything.
His first feeding is due to be today so we'll see how it goes.
I was also thinking a UTH on one side and a lamp on the other...