i bought a cheap one and it kept falling aapart and the inner one dropping onto the sand - total waste of money so I replaced with a magnavore and it even cleans corraline off the glass - love it.
MMMMMMMMMMMMMagnavore!!!! If you get one, the best prices I've found are at Custom Aquatic. I paid $99 for the Mag VI. Get the one that is recommended for your glass thickness, otherwise you'll have trouble moving it across the glass.
I leave mine in the tank all the time, parked in the corner and the back of it is covered in coralline now. It'll turn corners nicely so you don't even have to put your hand in the tank to use it if you just leave it in there.
Oh, and these buggers are strong. Don't get your fingers between them.... (Eeeeeeyow!)
