Using cooler for cooling water reservoir

[Morrey]

I have a 150 quart (37.5 gallon) Igloo cooler that I'd like to use for a closed loop cooling water reservoir instead of allowing outlet water to exhaust on the ground. I plan to use a 260 gph variable output fountain pump with 5/8" line to form the closed loop system.

Will this amount of water heat up quickly when heated water is returned? I can float frozen water bottles in the water to keep cool if suggested, realizing I want to maintain more or less constants temps and not rapid highs and lows. Or periodically drain some of the water and refill with cool source water.

What is the water temp suggested to provide adequate cooling? Is my proposed method more or less a "standard" way of utilizing a closed loop system to be water conservative? Thanks!