I am using Eco-Earth as a substrate right now. I have a thermostat on it controlling 2 different Zoo-Meds, one is brand new and is staying right around 97(89-92) through the substrate and the other will drop down to 80s and has gotten up to around 90 at max today. So I am thinking it just has to be the older Zoo Med crappin out on me. I see a lot of flexwatt for rack systems but how good is it for a tank? Since the only thing that is carried around my area is ZooMed stuff I will probably end up ordering something anyways. Thanks for all the info!