Mine is around 50-55 this time of year and the mag takes about 6 hours to get it to that temp mixing 25 gal
. During the summer it only takes about 2-3 but still with that pump it's a perfect 79-80 without getting any hotter anytime of the year.
I just lucked out because I've always used the trashcan and used to use a heater & powerhead but got tired of scooping out the water with a 2 quart pitcher.
I ran the pump one night without the heater going and woke up the next morning to 79 degree water. I also tested running the pump for 4 days and it never got any hotter.
I have 20 ft of hose to work with and a 4ft head so I'm getting around 600 GPH
out of it by the time it gets to the tank. I slow that down slightly but overall it only takes me 10-15 minutes to do a 15 gal pwc
I use a 15 ft ON/OFF extension cord
to turn the pump on/off which works really well.