Well, ofcourse if you do heavy maintenance on anything, it won't really be doing what everyone says it would, as far as giving off nitrates goes. As for that sea star.. that really is not a good place for it. It's called a sandsifting sea star for a reason. That CC can damage its body, as well as many of its tube feet. It may not be showing any signs of distress or damage right now, but prolonged use of the CC with that type of sea star is only asking for trouble. And yes, i would advise against CC.. but that's just MY opinion. You can do whatever you feel is best, and just see how everything fairs out. Sand is just easier to take care of, in our case, and in the livestocks case. Things like nassarius snails, plow through sand and eat detritus and keep up maintenance on the sand for you. As well as other things like gobies, some blennies, and some shrimp. I can assure you that if that sea star was able to sift through sand, instead of dried up pieces of coral, it would be alot happier. Not even going to go into the discussion of sandsifting sea stars in aquariums..
But overall, if it was my tank.. i would be switching to sand the first chance i get. And im sure alot more people here would back me up on that.