Split drain or split return?

[SeaHorse_Fanatic]

Change your pump. The Mag12 is notorious for its heat production. My friend's Mag12 will raise a 50g barrel of water change water to over 90F overnight.

For that size tank, a Mag7 or Mag9 (or equivalent pump) would be plenty.

If you want to test it out, fill a large container or tank with water, add some tubing onto the outlet to keep the water inside the container, then plug it in. Check the temp before & after to see how much it raises the temp. If it shoots up the temp, this will become a major problem in the summer time.

Just a word of warning.

Anthony