Knop S IV Calcium Reactor and pH Controller

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Aquarium Advice Activist
Jun 3, 2005
Murrieta, CA
I purchased the Knop S IV and am curious how to set it up. I also purchased American Marine Inc. pH controller. I see the pH probe hole on the top of the Knop S IV, I was under the impression you used the pH probe and controller to check the pH of the tank water and that adjusted the flow of co2 into the Knop reactor. But now I seem to be reading that you use pH controller to monitor the pH inside the Knop reactor or at least the effluent output, to keep it between 6.0 and 6.5. Is this correct? Also, does the larger media in the second small chamber on the S IV ever need replacing? If so, how do I replace it as I don't see a way to get it open as it appears glued together.

Hyperlink to my pH controller:

and Knop Reactor
Measuring effluent will give you faster feedback on the system than measuring the effect on the tank.

Did the reactor not come with a user manual?
Yeah, they're in a sort of broken english translation from German, so it's not like reading American written instructions... I spoke with a tech from American Marine Inc, and he agrees, measure the effluent with the controller.

I can only imagine that Bob Fenner didn't really understand my question, but I emailed WWM the same question and he said to measure the tank. He must be thinking it was only a pH probe, not a controller combo...

Can anyone make any sense of this? I don't want to respond to him again and upset/sound like a total idiot (This is his second response)

Thank You Bob, I got a response from American Marine Inc, and they stressed
that sense this is an alkalinity reactor (in reality...)
<... okay>
that it was more
important to monitor the pH inside the Knop S IV reactor as, "too low would
turn the koralith to pudding,
<... no... not possible. The KH of this source of calcium carbonate and carbonic acid...>
and too high a pH would do nothing". I have
elected to go with an aquamedic kalkreactor with an auto top off and doser
pump for the night time. And got a second pH monitor only (not a controller
this time) and salifert Calcium and KH tests to keep track of things inside
the tank (along with the Knop effluent). Trying to do things right this
time =;)
<Real good. Bob Fenner>
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