Well, I finished my DIY bipellet reactor. To be honest, it did a fine job...I just wasn't totally satisfied with it.
I've decided to go for a larger cylinder for the reactor. I was using a 3.75" OD acrylic tube. I think I'll be going for a 5 or 6" OD tube. At a foot height, the volume in there will be more than enough for a 300g tank I plan to upgrade to at some point. Also, although silicone worked well to bond the acrylic to the PVC
I just wasn't too satisfied with how it may or may not come apart in the future. I'll definitely be using all acrylic + some Weldon #16 on this build. It may increase the price a bit; but well worth it for peace of mind.
To be safe, I'll be going all acrylic on the reactor and using two 1/2" bulkheads for the in & out lines of the reactor.
A few notes so far:
1) A bottom plate is not a must need for the reactor. The biopellets had very good fluidity without a bottom plate to push water in all areas of the reactor.
2) Filter floss/sponge is not needed below the top plate of the reactor. With 2 ball gate valves (before and after the reactor lines), the level of control is more than adequate to make sure the top level of the biopellets are well below the top plate.
3) I tied my Mag9.5 return pump into the reactor line. Experimenting with different amounts of flow, I've found the best fluidity to come from using the same PVC
width for both the in and return lines. I've seen other reactors use a 1/4" in/out line so I used 1/4" tubing for the return line to begin with. I didn't like how well I could regulate the flow with the 1/4" tube valve. Maybe it was the manufacturer or not; but using a 1/2" PVC
ball valve gave much better control than the 1/4" tube valve.