How do CaRx flow rates affect effluent potency? | BRStv Investigates

Before taking down my CA Rx (mid-2018), I maintained a constant low flow with a lab grade pump, and adjusted the CarbonDoser bubble rate based on the Alk of the aquarium. I did monitor pH in the CaRx and it ranged in the area 6.4-6.6 but, I did not control on this value.

The CaRx recirc pump failed for the 3rd time in 6 years (about a 24 month life span) and I took this opportunity to move to Kalk dosing. The result is that Tank pH has increased from running 7.8-7.9 to now runs in the 8.0-8.1 area...note: this is also the time I focused on ICP testing and trace element adjustments...I see a clear and corresponding change in coral growth due to this set of changes.

I'm strongly considering re-starting the CaRx and looking forward to info from this series before doing so.

Thank you for the fantastic experiment.

Does altering the max saturation matter when you are holding the pH constant? I'm a bid dubious of the hypothesis. Looks like it's a show down between the reciculating pump and Kamoer, looks like kamoer won!

I personally fee the graph is flawed.
You need to have the Y axis as Total dKH and x axis as flow rate. Using just the dKH/ml does not convey a clear picture.

Joe Grubbs said:

Before taking down my CA Rx (mid-2018), I maintained a constant low flow with a lab grade pump, and adjusted the CarbonDoser bubble rate based on the Alk of the aquarium. I did monitor pH in the CaRx and it ranged in the area 6.4-6.6 but, I did not control on this value.
The CaRx recirc pump failed for the 3rd time in 6 years (about a 24 month life span) and I took this opportunity to move to Kalk dosing. The result is that Tank pH has increased from running 7.8-7.9 to now runs in the 8.0-8.1 area...note: this is also the time I focused on ICP testing and trace element adjustments...I see a clear and corresponding change in coral growth due to this set of changes.
I'm strongly considering re-starting the CaRx and looking forward to info from this series before doing so.

Click to expand...

In upcoming tests for CaRx's, I plan to test the effectiveness of various ways to increase pH before the effluent gets to the tank or other ways to mitigate low pH in the tank.

ispookie666 said:

Thank you for the fantastic experiment.
Does altering the max saturation matter when you are holding the pH constant? I'm a bid dubious of the hypothesis. Looks like it's a show down between the reciculating pump and Kamoer, looks like kamoer won!
I personally fee the graph is flawed.
You need to have the Y axis as Total dKH and x axis as flow rate. Using just the dKH/ml does not convey a clear picture.

Click to expand...

I think the common understanding is that the max saturation (with the pH pegged) will decrease as you add more flow through the reactor, due to a perceived less contact time with CO2 inside the reactor. In the first CaRx test we sought to find out what those max saturations were at each pH setpoint (6.2-7.2) and then armed with that info we sought to challenge that the max saturation would decrease with more flow (~"less contact time").

In this case, the graph shows the Y-axis as total dKH of the effluent output from our baseline, and then what that total effluent dKH was after running the reactor for 24hrs @ 20mL/min; then 24hrs @ 40mLs/min; 24hrs @ 60mLs/min... and so on. We can see that from the max saturation baseline for both 6.4 (23.1dKH) and 6.8 (40dKH) that increasing the flow by 4x-20x there is a change to the max saturation, but pretty nominal at best.

Using mEq/L might make my point a bit clearer. The total alkalinity would be flow rate x mEq/L so for the higher flow rate your total alkalinity output would be higher even if your alkalinity drops.

I use an aquacare turbo. I peg flow and pH and then just adjust the time the reactor runs. The reactor runs based on co2 saturation with a float switch. Its internal pH is about 5. Flow rate is 70ml/min. Only runs 10 hours a day at the moment.

The media is a spherical pharmaceutical grade calcite.

The reactor has a chamber to increase the effluent pH back to 7-7.3, using a counter-current airstone set-up, then it has a de-sedimentation chamber at the top, before it hits the tank, so the display pH never drops below 8.



Works pretty well on my 90-gallon sps tank:

I have done a bit of jiggling around with your data and converted it to meE/L and using the flow rate used to calculate the output per hour.
X axis is flow rate per minute
Y axis is Alkalinity ouput in mEq/L/Hr

If you are looking to increase the output of the reactor - this graph probably puts things into perspective