if your ambient house temp goes below mid-high 60's, you won't need a heater. even tropical SH should be maintained below 74*F due to their propensity for developing bacterial infections, which are often fatal.
if the temp of your setup goes above 74*F, i highly recommend a chiller, especially since the warm weather is upon us.
also, i highly recommend the use of live macroalgae in your DT, as it harbors pods, gives the SH hunting/hitching areas, and aids in nutrient export (SH are very hard on water quality).
also, you may consider dropping a length of open-ended rigid airline (maybe even two) down the back as bubblers since the tank is deep. i prefer airlines to PH's in SH setups, as there is no way for them to get their tails stuck in them. the SH may also hitch to the tubes for a "bubble bath" to clean themselves off.
HTH