I had some diffusion stone issues, but it seems to be working OKAY now, however, the stone is still not producing a lot of bubbles. I am reading that smaller/mist bubbles are better, but it's not producing that many. To conduct an experiment, I tried a different aquarium pump to my diffusion stone and it produced NOTHING even though it powers my 30 gallon fish tank just fine. So, my question is, for those of you that aerate wort with a diffusion stone and aquarium pump - NOT straight oxygen from an O2 tank - which type of aquarium pump do you use? My setup is something I'm borrowing from a friend, and the pump might be really old, however, 3 months ago it did create enough aeration to result in overflowing foam from my primary! But, since then it's been very modest in its output. I have boiled the stone and when I hooked the stone straight to an O2 tank at my local home brew store, it did produce bubbles, so I think it's just a matter of upping its power supply (thus the question of which fish tank pumps do you suggest).