Understanding the Calcium reactor: Adv question

[spsal23]

I've been in the hobby for a while and i'm using a korallin reactor c1500 (smallest model) with the ph probe built in the lid. I'm using the regular sand reactor media from carib sea and using the Digital Aquatics controller to turn on and off the solenoid.

The question is: I've dialed in my pH initially at around 6.8-6.78 in the reactor, and this balances my alkalinity at roughly 160-164.

A few days later the pH in the reactor continues to drop. I have not tweaked anything and the pH in the reactor has fallen to 6.64.

I've started having a few sps issues slight stn. Can anybody figure out why the pH is falling in the reactor?

Any help would be greatly appreciated.

[sgolden]

i'd say too much co2...when the solenoid opens it should be a very slow release of bubbles...like 1 per second or so...perhaps the probe is bad..or needs to be calibrated....how much effluent is flowing out? a higher flow of effluent and less co2 intake may help...if the corals are stressing , i would take it offline....good luck

[Flamehawk1221]

The bubble count is too rapid. Eventhough the pH controller is shutting it off based on your 6.8 value, it is reading the the pH before the last bit of CO2 that last enters the reactor is able to dissolve into the reactor's water. Try lowering the bubble count so that the selenoid doesnt cycle on and off too quickly.

Hope this helps.

[chuckreef]

I agree with the above. I also notice my Ca RX is not linear in operation. That is, when it is full of media the water volume (in the RX) is smaller so the pH is higher and the reactor effluent is weaker. As the media dissolves and the water volume (in the RX) increases, for the same rate of CO2 introduced the pH gets a little lower and the reactor effluent becomes more potent. You can actually see over a few weeks time that the media leve drops faster in vertical inches when the rx is down to half-full or less. So, I ahve adapted to never filling the RX more than 2/3 full (leave some more water volume in their), and to re-filling the media more often to keep things more stable.

I should add this pH on the effluent, not in the rx per se. Obviously, if you add more CO2 toa smaller volume of water, it should yield a lower pH.

[scottwhitson]

No one has mentioned that the effluent rate leaving the reactor could have slowed down causing the drop in PH. That is the biggest problem I have with my reactor is trying to find a reliable way to control the effluent rate out of the reactor.

[Lutefisk]

No one has mentioned that the effluent rate leaving the reactor could have slowed down causing the drop in PH. That is the biggest problem I have with my reactor is trying to find a reliable way to control the effluent rate out of the reactor.

:thumbsup: Often overlooked.

Unless you can control BOTH CO2 input AND effluent flow you'll be chasing values all over the place. That being said, don't get hung up on 0.14 pH swings or deviations. As someone mentioned, this will occur as the solenoid valve switches on and off. Also, in light of the fact that our pH probes are drifting from their calibration over time and that many calibration standards aren't all that accurate to start with, use your pH readings as a valuable rule of thumb rather than an exact number to hit.

If your SPS is starting to look bad I would suggest looking at problems other than your CO2 reactor (although it could be related reef chemistry issues such as alkalinity and calcium in your display tank).

Paul

[Henry Bowman]

Agree with above regarding effluent. Not making sure it is consistent will have you chasing your tail.

Dont try to control the effluent on the output side of the rx. the valve will continuously clog and be hard to adjust. Control the water coming into the reactor from the tank to adjust the flow.

My .02 cents FWIW

[Lutefisk]

Dont try to control the effluent on the output side of the rx. the valve will continuously clog and be hard to adjust. Control the water coming into the reactor from the tank to adjust the flow.
My .02 cents FWIW

Controlling effluent on the input side also helps you control the CO2.

When the output is free flowing the pressure within the reactor, into which the CO2 is being injected, will be much more stable. This minimizes fluctuations in the pressure difference (delta P) between the CO2 reactor output and the reactor pressure resulting in more consistent CO2 injection.

It's a win-win

Paul