you could probably control it based on temperature if you have an RKL or other controller.
I am not sure on other brands - I do know that the common complaint regarding chillers is they tend to be noisy. You often get what you pay for in this hobby... I know that is of little consolation when looking at a $700 purchase to lower your water temp 3 degrees
Have you considered maybe just trying to run some fans to blow cross the surface of the water, or maybe go LED
for lighting to reduce heat? You might be surprised, you may not have a need at all for a chiller.