@100% on my lights I can only drop to 78f. I am good with that. water temp at the most is 74 f. I use hydroguard and no problems.
100% Cake? what kind of light(s) are you using at 100%?
ac infinity Evo 8 . 100% percent is when the dimmer is turned up as far as it can go, so I would be operating at 100% of what it is capable of producing