Gen, you can buy lava rock at any home improvement store...I'm going to take back what I said earlier about not needing the airpumps and stones...I think this made a small algea problem very bad since I'm not running any kind of beneficial bact. like a stream to take care of the algea. It's also very important to have water temps around or below 70 degrees...and take into consideration that your pumps are blowing the hot air from your room into your buckets if the pumps are inside the room. That is why it is also fairly important to keep temps in room as low as possible as well. I've learned a lot more since going to this recirc. system, but I think next round will be MUCH better...and will be all ONE strain...White Rhino...also with a recirc system such as mine, if one plant gets algea or disease, they all get it, so just keep this in mind...the system, room and res's need to be VERY clean and maintained clean (which isn't hard to do) for the system to work well...it's def. not for the lazy until you get it super dialed in.
-sD