I am currently using an external reactor “Rex” design attached to the outflow of my filter. I also have a Milwaukee PH controller. I have had this setup for about a year now and has been working fine. Controller was set to shut off at 6.4. Probe calibrated every month. For about a month now, the controller has not been shutting off when it reaches 6.4, when I get home in the evening it is still on, so I switch off the controller and turn it back on and it then shuts off. Any idea why it’s been doing that? I checked everything, re-calibrated but same thing the next day. Could something be wrong with the controller?

I know that many are getting rid of their controllers but it’s so convenient, shuts on and off on its own, well except for now. I have spent so much money on it and don’t have the heart to put it aside, unless I am convinced that the system would work better without it.

As for the reactor, it works fine but uses up too much gas. I have to do at least 7 to 8 bps for it to reach 6.4 after 4 to 5 hours. The cylinder has to be replenished more often. When I was using the generic glass diffuser, I could use the gas for a much longer time at 2 to 3 bps.

I am now thinking of getting rid of the reactor and getting the ADA beetle 40, I can’t get the parts required to make the diffuser/reactor that Tom mentioned. Are the ADA glass diffusers really good? I don’t mind the cost, but want to know how good they work?

This does not add up, because it always takes a certain amount of dissolved co2 in the water for the pH to drop from one level to another, this does not depend on how you dissolve it.

What value does it show when you get home? the controller usually has some hysteresis and that often means that it goes at least 0.1 lower than the set point before shutting of.

If the value is not that far from your set point i should guess that your plant mass has grown and the bubble rate or disseverment is only high enough to just hold the set pH.

This also would be a reason for the higher need of co2 gas.

Well then when I set the bubbles to 2 to 3, it takes forever to reach 6.4. Perhaps the reactor is not efficient enough?


When I get home it is at the set PH, i.e. 6.4 or 6.3, but it won't shut off. So I thing you maybe right, it could be that the plant uptake maybe huge and the reactor is is not big/long enough to diffuse at a high rate. Actually come to think of it, the first reactor I made was about 24 inches long and I never had a problem, then I modified it to about 18 inches, and I think I've been having the problem since then. Maybe I should go back to the longer one.

I did a heavy pruning last night, I'll see if that helps when I get home, you could be right.

But I also want to try the ADA beetle 40. It's nice and neat.

When you have to use a lot more bubbles per second to get the amount of CO2 you want in the water, the first thing to check is always leakage. It takes very little leakage to double the usage of CO2 from the bottle. Since a diffuser seems to be more efficient in CO2 usage than the Rex reactor, the logical place to look for a leak is in the connection to the reactor or at the top of the reactor where a gas bubble should be collecting.

Well after the huge 'chop chop' pruning, it's cutting off now at 6.4. So I guess the set rate was holding up.

But thank you VaughnH I will look at the entire line and check for leaks as well.

Nice to hear that it helped.