I'm not sure if I'd use copper coil, as the copper would taint the water and your inverts would die and the fish might get sick.
One of the things that water conditioners detoxify is copper in the tapwater from your house plumbing.
I saw someone's home made cooler once for a north sea marine setup where the water had to stay at around 2 degrees celcius. It was a standard small chest freezer with two holes drilled in the top and placed under the tank.
All the pipework, the pump and the sump were in the freezer taking water from the tank, cooling & filtering it inside the freezer before returning it to the tank.
It worked like a dream and the freezer only cost about £70!
One of the things that water conditioners detoxify is copper in the tapwater from your house plumbing.
I saw someone's home made cooler once for a north sea marine setup where the water had to stay at around 2 degrees celcius. It was a standard small chest freezer with two holes drilled in the top and placed under the tank.
All the pipework, the pump and the sump were in the freezer taking water from the tank, cooling & filtering it inside the freezer before returning it to the tank.
It worked like a dream and the freezer only cost about £70!