Nice dude. I love the "vortex" style brewers. Much better than stones and a stocking. I built one but it's a 6 gallon beer brewing bucket. I used 2" schedule 40 on mine, and i'm using an eco 5 commercial pump. I only have 1 airlift now instead of 2. I found that 1 was better with my pump. When I had 2 lift on it, they would alternate as if my pump couldn't push both equally.
But he'll yeah, anything can go in as long as it's small enough in size as to not get stuck. I've even thrown grow stones in there before to make a "perch" for fungi to attach. Any dry ammendment!
Look for a lid tho, this will help reduce splash and return any evaporated condensation back to the brew. I've lost volume before in the past when I brewed in warm temps and without a lid.