ReefSparky has laid it all out, follow his directions now and you should gain the upper hand on it. only thing I would add is do a water change also. Star fish is an asternia if is white. My RODI unit isn't mounted or plumbed, I built a small stand and hook it to the bathroom sink in my basement when I need it. then I wrap it up and put it away. I agree with reefsparky purchase a TDS meter, Air Water and Ice has them for as low as 15 bucks. test that water if it tests out at 0 then by all means use it but if it tests any higher then stop using it and get a RODI. They also have RODI called the Mighty Mite for people with small tanks which would be plenty.