I also wanted to add that in my old tank i was looking for a sand sifter as well. Ultimately i ended up stopping the search and now i just clean it myself once a week.
I looked into the twin spot, sand sifting stars and who knows what else. But at the end i realized that i couldn't find something to keep the sand bed clean like the way i thought i could. Also I had the problem of a lot of sand sifters are predators of creatures I'm trying to raise and breed in my tank. I am a member of projectdibs.com and there we try to breed a large number of mini star fish, snails and worms so i had to be very careful what i put in my tank. Just something to think about.
