Hi sooner.
What is the temperature pull down you need?
I have installed and used micro and mini chillers (1/10HP, 280W and 1/4HP, 650W).
It is easy to install and do maintenance, given that you have a Wet/Dry
sump filter.
A bigger than needed unit will cost more to get, but will keep your energy bill lower.
For a 4 footer tank, with 40 to 60 gallons of water, a 1/4HP mini chiller with a water pump or
powerhead rated at 300 to 600
GPH would do the work fine.
If you keep a smaller tank, say in the 20 to 30gal, 2 or 2.5 footer, a 1/10HP micro chiller will do the work with a 250 to 450GPH water pump or power head.
For tiny tanks, a thermoelectric chiller might do the work if your pull down temp is not too much.
Pepe
Santo Domingo