do u have a tds tester id check quality of ur ro water to start with. start at the supply and work forward. i keep all me 55g barrels at 50deg with an 8inc blue airstone no movement pump. and i keep it in the barrels for months at a time with no blooms. as for keeping the res at tank temp i think ur asking for trouble with algae. with my experiences. i heat my water 6 hrs before using it.