Heating help needed

Big K

Reefing newb
Hello fellow Wetarms!

I have a 55 gallon reef tank with a 40 gallon sump (in my basement) and am having issues regulating the temp. I have three 150w Cobalt Aquatics heaters in the sump in three different areas. The temp fluctuates up to five degrees when all three are set at 80.

I am adding a 110 gallon FOWLR and a 20 gallon frag tank soon, so what will I need to do to keep the system steady? Do I need to insulate the lines going up/down?
I built my own controller a long time ago to control my heater and my fans. My temp never fluctuates more than +/- 1 degree or less.