I took an old weight belt and cut it into something like 35cm/14" pieces, which were then sewn into an "X". I use a hose clamp to attach it to the bottom-now-top of the tank, and stick whatever size weights I choose underneath. Voila! Cheap, compact, effective, flexible, lightweight, shoulderheight and secure. Credit to John Priestley, he came up with the idea.

In the pic you can see me walking on water in Scapa, with said weight attachments.