I currently have a 150 watt heater for my 29 gallon tank I'm adding a 20 gallon sump I have not added water to the sump yet but I guess it will add about 10-13 more gallons of water do I need to add another heater?
I would not recommend a 150 watt heater for a 29 gallon. In all cases two smaller heaters are better than one oversized heater. I understand, it's an additional expense though.
I live in Kansas City kansas
Temp of the room is usually 72 or so
I want the tank to he at 79
I have a 100 wat heater and a 50 eat heater laying around but I use the 50 when I mix salt or acclimate fish
For heating 30 gallons just 7 degrees a 150 is overkill. The concern I have with that is when a heater fails it sometimes fails in the on position. 150 watts is going to raise the temp high quickly in your circumstance.
Two smaller heaters will be effective and not nearly as dangerous.