what is the best sand-sifter?

[fresh]

Hi all,

I want to get me a sand sifter on the boxing day sales, but I don't know which one!!! I don't want to add anything that will kill all the good stuff in my sand and then starve (such as yellow-headed goby). I probably want something that mostly eats algea and stirs the top part of my sand. Probably a big NO to a sand-sifting star because from what I heard they decimate all life in the sand.

I also don't want anything that will end up digging under the rocks and causing a rock-fall!!!

Any suggestions? I heard about conches, is that a good option? What about cucumbers? Are they reef safe? Just let me know what has worked for you before.

I have 10 or so Nassarius Snails but they are not doing the job properly, so I just thought about adding more help.

Thanks
fresh.