I'm using a flood and drain so the air pump is just suplimental. My 23" bubble wand (non flexible) began to clog about half way down the length of it after about 3 years in an aquarium. I haven't had enough time in hydro to witness one clog in nutrients.

I figure they clog from dirty air being pumped into them. But again, they're so damn cheap, you could afford to warehouse them.

I'm not sure, but it appears that the smaller diameter tubes provide smaller bubbles. My wand is very thin, about the diameter of a pencil and it gives me a tank full of bubbles. I broke it while stiring the reservoir (twice). Just capped the end of the shortened piece and back in business.