Question, i just set up a 70 gallon tank with a 20 gallon sump and a 17 gallon refugium. I have a 5" dsb and a skimmer that will handle a 200 gallon system. I use a UV light and my sump is a wet dry filter filled with LR. I have about 130lbs of LR in my all my tanks. some in each. That's my set up, anyway the question i have. Do i need to do water changes? My water numbers are all OK. Should i do a water change? I have heard both yes and no. I only have one frag in the tank and 3 fish.. let me know what you think