1 200w jager on my 70. No overheating issue and keeps the tank at 78.3-78.5.

I have 2x500 W titanium heater on my 250gal no issues keeping my tank in the 25c range overnight. My Nest house thermostat is programmed to drop the temp to 19c during the night. No issues keeping my tank in the basement toasty.

I got 600 gallons of water now, before we were running 3 500w heaters and they ran all the time. House was at 18 Sump is covered tank enclosed in canopy. In the winter we turn the heat up to 22 in the house now and the heaters hardly run keep the tank at about 25