I bought a Spectrapure that had the reserve tank (so we could use it too) and plumbed it to the refugium with a top-off system to provide continuous makeup for evaporation losses. My next project is a mix tank with a float valve that I'm going to put under the counter next to the tank and T off of the RO
line to keep it full. I'll put a small pump in that runs it in recirculation to mix salt and I'll plumb it back to the tank overflow. I have a 120 gal
tank, so I'll make it about 30 gallons. Just have to figure out where to put the trap door for adding salt.