Before building my overflow idea (which now I can't imagine having a tank without it, and will mod all future tanks likewise) I had a few ideas that I rejected, but close runners up as far as making tanks anemone proof. Here's some ideas to cover a powerhead.
Expensive.......
Black Acrylic, Weld-on
Cut and fit acrylic sheet to form a 3 sided rectangular box twice the size of the pump you'll be using, cap the top and bottom with black acrylic. You'll end up with what looks like a black plastic box, with no lid. Drill one hole on the lower end of the face of the box to stick the pump out-put through. On the opposite end if the box, drill many smaller holes on the top and 3 sides of the box. On the back (open side) attach a small strip of black acrylic pretty much anywhere, and use that strip to place magnets to secure to the side of the tank.
Cheap.......
Go to the dollar store, K-Mart, Wally World etc. and get a small colander (Pasta Strainer). Handle-less works best, but if it has a handle, just cut it off. Paint it black (or buy a black colander to begin with), drill a hole the size of your pump's out put (slightly smaller actually so it's held on to the pump via tension) alond with a notch in the side for the cord, and you have an anemone proof pump.
(As a side note, as ghetto as this sounds, I actually used this as a temporary fix a few years back, and ended up with it being semi-permanent because it looked great. I did a few more mods to mine, like very evenly cutting everything from the colander but the slotted portion, and then dyeing it black. Mine was big enough to hold two pumps which is all I needed for my set-up, and nothing ever went through the veggimatic, which is what this thread is about.)