I have a 75 gallon aquarium with full screened lid and have a 150 watt heat bulb and all other necesities...my problem is i cant get the temp past 85 degrees on the warm end and 78 on the cool end...she spends 90% on the cool end though...i am going to switch to a UTH and thermostat that way i can control the temp and because the lamp is killing my humidity...my question is are these temps fine and also what size UTH do i need...the ones at the shop here dont say what size tank to use em on...do you think a 12x12 inch one will be good or do i need to go to the next size up?