I have a Rex Reactor that was 2" and 2' long. The problem I had with it, since I had to run the co2 so high it would stop water flow. I had my return line split to lower the water flow into the reactor. After a couple months I noticed that there was no water going into it. So I decided to build a Creges Reactor and I'm getting huge co2 bubbles. I did add media balls to it to help breakdown the co2 but that doesn't seem to be working. I do have a 90g with a sump tank and my return pump pushes 900gph.