Alkalinity out of control

[bosworth]

My Alk is at 15 and my Ca is 475 and my Mg is at 1300 Sg 1.026, Salt is I/O Reef Crystals. My total system volume is 150G.

I just recently tested my MG and found it low 950, so over a 3 day period I dosed Kent Tech M per the Flash Calculator to raise it to 1300.

On the second day of dosing I noticed that my Ca started to drop so I dosed SeaChem Reef Advantage Calcium per the Flash Calculator. I was aiming to tkae it from 400 to 450 but it over shot it.

On the third day I checked everything again and my Alk has jumped from 12.0 to 15.0. I have always ran on the extreme high end of acceptable levels but this is way too high.

I use a GEO Calcium Reactor for Ca and Alk, and a Geo Kalk Reactor for all of my top off mainly to help elevate PH.

What adjustment do I need to make to my Ca reactor in order to lower my Alk level? This is my only option.

[Randy Holmes-Farley]

The increased magnesium may be greatly reducing the demand for calcium and alkalinity in the tank by reducing the abiotic precipitation of calcium carbonate. Hence the alkalinity rise.

Reducing the reactor output is not your only option (stopping or reducing the limewater is another), but it is what I'd start with. I'd back off on the CO2 delivered to the reactor by at least 50%. Maybe shut it off entirely for a while and let alkalinity drop. :)

[bosworth]

Thanks Randy. I am afraid to stop the limewater because I would see a significant drop in PH. I will definately turn the CO2 off for a while. I cant reduce it because its on a solenoid attached to a PH monitor, the best I could do is run the reactor at a higher PH level.

Do you think I should run the reactor at a higher PH level or just run it w/o CO2?

Also I understand that you can very the Alk/Ca ratio by adjusting the effluent output of the reactor. According to GEO if you increase the effluent drip rate you are increasing the reactor PH and lowering the Alk output. Is this right? I don't really understand ow this works if the CO2 is feed via a solenoid on a PH monitor.

[Randy Holmes-Farley]

Yes, when you restart, definitely either set the pH higher, or reduce the effluent flow rate. :)

Also I understand that you can very the Alk/Ca ratio by adjusting the effluent output of the reactor. According to GEO if you increase the effluent drip rate you are increasing the reactor PH and lowering the Alk output. Is this right? I don't really understand ow this works if the CO2 is feed via a solenoid on a PH monitor.

Not really. Tank water comes in with a certain amount of calcium and alkalinity. Then any dissolution that takes place adds calcium and alkalinity in the ratio of about 20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity. More CO2 means more of both equally in that ratio. So there is not really any independent adjustment, but bear in mind that alkalinity is what shows up first when overdosing or underdosing because there is a huge reservoir of calcium in seawater. :)

[bosworth]

Thanks Randy you make it so simple.