I’m not a hydro guy but I can tell you how to make a cheap chiller. Get a old bar fridge and some hose or copper pipe and coil it inside the fridge. Connect a pump and let her circulate the water from your rez, should work pretty well. I used a setup like that on a cold water aquarium I had years ago and it worked well and cost me not a penny as I had the materials laying around already.
Hope that helps