I went to the dollar store and got a package of those chip clips. They work great clipping down veggies and sinking them!
And there's a little pice of magnet on it, so when it's time to get it out, it sticks right onto the net!
My snail has been ignoring all the veggies I put in though...I've tried a few... I guess I have to go get some zucchini for him because I think that's what the LFS, where I got him, feeds their snail.
So, so far, he just goes up and down my tank, which has NO algae... (It's a cycled tank that I do either a 25% or 50% depending if I waited a week or two.)
However, he shares algae wafer with the cories... that is... if the piggies on top don't see the algae wafer first! Usually I drop the sinking wafers (Both algae and the ominvorous ones.) behind the plants as to "hide" them from the piggies!

It works! Usually I feed the starving mass on top, and while their too busy stuffing their face, start sneaking in the sinking food!