Here is my version of your awesome idea. I had some extra marinepure cubes laying in my sump. Do you think I will have an issue using some of that in the reactor?
Solidly built, must be earthquake proof in mind . MP should do the job but I am not so sure about the leaching I have read somewhere.
The outlet pipe is kind of huge BTW. We try to minimise O2 exposure inside the second reactor. A much smaller pipe/hose is preferable as the flow is quite low.