Reef Octopus Calcium Reactor question

[Richard Schmidt]

I have a 93 gallon cube with 30 gallon sump.
This my 4th new setup tank. All other setups used the same Koralin (sp?) reactor. Calcium was always above 475 on my other tanks.
Bought a Reef Octopus CR140D external calcium reactor figuring it would handle this setup (supplier even said they thought it was overkill for the set up).
This tank/reactor has been running for over 6 months now.
So far the best I have gotten out of this reactor (checking at drip port into the tank) is 420.
I am running this reactor with a PH probe thru my cerebra controller.
I am using ARM media.
Read several posts saying ARM starts reaction at about ph of 6.5
I set my controller to run the reactor at 6.4 just to be sure.
Still getting nothing better than 420.
How do I tune this thing? I know it can do better, just not sure how to tune it.
CO2 running about 30 bubbles per minute (when controller calls for it), output drip rate around 20.
Any input appreciated, I know it can do better, I just don't know how to tune it.
Thanks

 

[Reefing Madness]

 

[Breadman03]

Is the reactor maintaining your tank parameters adequately?

We can basically adjust the pH and effluent rate of the reactor. Increasing CO2 will drop pH and increase the saturation of elements in the effluent, though dropping pH too far can cause issues. Alternatively, increasing the effluent rate will increase how much is getting pumped into your tank.

I've never actually measured my effluent parameters. I just test periodically to ensure tank stability.