Hi,
Can you insulate the tanks with foam board or cork or reflectix (sp?) or anything like that and cover over the top as well?
What temps are you manageing to get it up to already? Oh and what are you using to measure them (digital or analogue) and where about in the tank - this should give us an ide aof how much of a difference you have to make up.
Have you thought of plastic tubs as housing?
What size are both snakes and both tanks?
Can you tell us the aminient temps in the room?
dr del