Over the years I have seen many people post on Facebook and Fish Forums about how their pH is 7.5 and they don’t know what to do. While over time, this is certainly a situation you wouldn’t want to maintain, the first guiding principle should be to not freak out. This isn’t as bad as having say alkalinity at 4dkh or your reef tank at 68 degrees, there are methodical steps that can be taken to help you get this situation fixed, reversed, and remedied forever. Keep in mind that every situation is different and you may have to test and try out many of these to find a solution that cures your ailment.

Remember that even in the oceans, pH is one parameter that fluctuates every single day and by a decent amount.

First: Why NOT to freak out

What causes Low pH in a Reef Tank?

In a word, excess carbon dioxide (CO2).  Inside our homes, we breath, cook and have HVAC systems that all contribute to a lower level of oxygen and higher level of CO2 than you would find outside. The same can be said for reef tanks.

Impact of Low pH on a Reef Tank?

Its real effect is that low pH gives downward pressure to calcification as the dissolved CO2 is trying to basically act like a calcium reactor and dissolve your corals’ skeletons. In plain english, this means that over time, you will see slow to no coral growth in the tank. This does not mean you need to rush out to your LFS or to your favorite online retailer and buy a bunch of nutrients or “band-aids” to increase coral growth and pH in your tank.

Ways to Counter Low pH

First, make sure you have a solid way to even test pH. There are stand alone units like the ones from Milwaukee or Pinpoint or the ones that can be integrated into controllers like Apex or Digital Aquatics. The key here is to ensure you are calibrating the pH probes regularly (monthly) to ensure you are getting an accurate reading.

The first option we recommend is just to try and get more fresh air into your home. Opening a window, opening doors, etc. If you see pH increase and the swings diminish, then you know you are battling an issue with CO2 and not something else like stray voltage in your tank, possibly from a faulty heater or pump or some other metals that have leached into your tank.

Secondly, if you have a sump, ensuring your have a good bed of macro algae and a grow light is another quick step. The macro algae will serve two purposes by reducing your Nitrates and absorbing CO2. The light can either be run 24×7 or you can program it to be on at reverse times as you run your tank lights. This will help counter the pH swings. We’ve seen this narrow our pH swings from about .3 at night to about .2 \ .15.

A second option is to install a CO2 scrubber to the air line of your skimmer. This option is a little more expensive and depending on the CO2 levels near your tank, you may go thru media fairly quickly. The installation of a CO2 scrubber is very simple as you just need a canister (reactor), some scrubbing media and some tubing. The whole installation should take no more than about 30 minutes to setup and is a very easy solution to try. Once the CO2 scrubber is hooked up to your skimmer intake line, note the time you turn on the skimmer and observe any swings over the next 24 hour period to see if this helps increase pH. After the first 24 hours, check the CO2 scrubbing media, especially if you are using color changing media, and note consumption or usage. If you notice a significant amount of usage, then you are probably dealing with higher levels of CO2 and may want to try another option to keep costs down.

A third option is to run your air intake line outside to draw fresh air in directly to your skimmer pump. To do this, you will likely need to drill a hole thru the side of your house and then connect a lengthy piece of hose from outside to your skimmer intake. We have done this on one of our tanks and it helped raise the pH by about .15. The one suggestion is to get the largest diameter hose you can. We installed a 3/4″ OD x 5/8″ ID – 30′ hose on our tank. Before drilling holes thru the side of your house, run the air line outside thru an open or partially cracked window, and observe the pH swings over a 48 hour period to see if this is a solution to your problem. If the pH rises to an acceptable level or the swings diminish, you can turn this temporary solution into a permanent one.

If you live in the Midwest like us, then you know the pH struggle is real! On some of our tanks, we’ve had success with the option of running an airline from the skimmer to the outside. We’ve also seen marginal increases by adding the CO2 scrubber to the airline from outside, but we are still struggling with one of our setups where the sump and frag tanks are in a utility room with HVAC equipment and our show tank is upstairs in a room with a vaulted ceiling.

If you have any questions, suggestions or ideas you’d like to share, we’d love to hear from you!