Blowing off CO2 from calcium reactor to lower pH

[trilinearmipmap]

The pH in my mixed reef has run between 7.9 and 8.1 ever since I got my calcium reactor a few years ago, despite an Alk targeted around 10. I never saw ill effects from it and sometimes I've wondered whether the excess CO2 (low pH = excess dissolved CO2 in the water) may do the corals some good, as I have always assumed the zooxanthellae ought to consume CO2 like any other form of algae.

Lately I have upgraded the equipment - started with a better skimmer, now better lights (PowerModule) and getting better flow soon and installing a controller - to keep more of an SPS tank and I'm not sure of the benefits of blowing off CO2 to raise the pH to the more acceptable range of 8.1 to 8.4

Right now the calcium reactor output feeds into the sump after the protein skimmer and before the refugium. I have thought about either feeding the calcium reactor output into the intake of the protein skimmer, or putting a MaxiJet with venturi into the sump and feeding the calcium reactor output into the Maxijet to aerate it.

Possible upsides include better coral health and growth from the higher pH assisting calcification. I am worried about the possible downsides of less growth due to less CO2 for the zooxanthellae, and a risk of bleaching or killing off my SPS if there is a change from the pH which they have been used to.

If anybody runs an SPS tank with this lower pH range, or if anybody is taking steps to blow off CO2 please let me know your experiences and opinion.

Edit: the title should say to raise pH, not to lower pH, can't change the title now

[04scoobysti]

Be careful if you choose to blow off any CO2 to raise your pH. The first thing to benefit from my experience will be hair algae or other undesirables.

[Ya Dude]

How do you know its Co2 lowering your ph do you have a C02 probe or something ?

[fkshiu]

You could also drip kalk at the same time to raise pH.

[StirCrazy]

I ran at 7.9 on my SPS tank and it was fine. I wouldn't worry about trying to raise it unless you are having problems and you know its the PH.

Steve

[untamed]

Originally Posted by StirCrazy

I ran at 7.9 on my SPS tank and it was fine. I wouldn't worry about trying to raise it unless you are having problems and you know its the PH.

Steve

This is true, there is nothing really bad about pH 7.9. A bit higher is better...but hard to achieve. One thing you will surely see if you track your pH over 24 hours is that it goes way up in the daylight, and drops overnight. Minimizing that daily fluctuation would be a better goal than trying to move from a 7.9 avg to an 8.1 avg.

I've found it possible to reduce the nightly low by dripping Kalk only during dark hours. In fact, I can tell when my Kalk reactor needs new Kalk because the nightly pH low becomes distinctly lower when that happens. (Which happens like clockwork every 14 days)

Finally, rather than attempt to "blow off" CO2, I would recommend adding a second stage to your Ca reactor. Stage 1 of my reactor runs at pH 6.5, but the effluent is up to pH7.2 by the time it runs through my second stage.

One of the challenges with "blowing off" CO2 is that our homes tend to have a higher CO2 concentration than outdoors. Even outdoors, we've generally raised the CO2 concentration over the entire planet which is a contributing factor in the acidification of our oceans and decline in coral reef health.