How To Raise pH In Reef Tank Without Raising Alkalinity

By Harry RamosLast update: 2024-07-11
How To Raise pH In Reef Tank Without Raising Alkalinity

The main reasons for a significant pH decrease in a reef tank are either because of too much CO2 (whether in the water or in the air around the aquarium) or low alkalinity.

But if you find that the cause isn’t from low alkalinity, which means you can’t add more buffer into the tank, here is the best way to raise pH in the reef without raising alkalinity. Keep reading!

What Are The Ideal Ph Ranges For A Reef Tank?

How To Raise pH In Reef Tank Without Raising Alkalinity

To encourage coral growth, health, and metabolic processes, it’s important to remain a steady pH range within 8.1 to 8.4. The reason is at such a pH range, your reef tank has an antiseptic effect to boost your corals to calcify faster.

Buy a pH test kit and check the pH ranges of your reef tank these two times during the day:

  • In the evening right when the lights are turning off
  • In the morning right before the lights come on

For those who don’t know, pH should fall out at night and rise during the day, just like it takes a breath.

Why Is My pH Dropping In My Reef Tank?

The pH drop, in most cases, is because of the acid created by the production and reduction of ammonia. This substance is produced by the livestock in your reef tank when they eat food and release waste that then decomposes.

How To Raise pH In Reef Tank Without Raising Alkalinity

How Do You Dissolve CO2 In An Aquarium?

There are some common ways to lower CO2 in a reef tank:

Perform The Open Window And Door Test (up to 8.3)

How To Raise pH In Reef Tank Without Raising Alkalinity

The rise of CO2 volume in the air is caused by many reasons:

When fossil fuels are burnt. In other words, the CO2 volume raises highly if you cook frequently while the air ventilation capacity is poor.

CO2 is a byproduct of normal cell function and is gotten rid of from the body (both humans and animals) via the lung in the exhaled air. That means too many people or pets (like cats and dogs) in a house will raise the CO2 level.

This directly affects the pH of your reef tank. Opening all the windows and doors in your house is the simplest, easiest, yet most efficient way to dissolve CO2.

Use A CO2 Scrubber (up to 8.2-8.4)

But if keeping windows and doors opening all-year-round is impossible in your case, another easy way is using a CO2 scrubber.

It contains CO2 absorbing media and is designed to attach to the protein skimmer air intake. So, before the air enters the skimmer, it will remove a huge majority of CO2 gas.

This method comes in handy as nowadays skimmers produce a great amount of gas exchange exceeding what occurs naturally at the surface of a reef tank. But take note that some CO2 scrubber might work too well, which could raise the pH in your tank too highly.

To control this, there are two solutions:

Utilize the wye fitting but instead of attaching a valve, choose the one attaching an electric solenoid on the fresh air side (commonly found in more technologically inclined models)

Add a valve and wye fitting on the wye’s fresh airside. Manually valve back the fresh air in tiny volume until the pH level reaches your desire.

Out of the two popular methods as mentioned above, here are some other worth-noting options to consider:

  • Run an air-line outside (up to 7.9-8.2) – suitable for those people who are living in colder climates. But take note that if your area is sprayed periodically for mosquito control, it’s essential to put some carbon filter types at the air intake to avoid these chemicals from entering the reef tank.
  • Install an air exchanger (up to 8.0)

Growing A Refugium With Macroalgae (raised pH ~0.05-0.1)

How To Raise pH In Reef Tank Without Raising Alkalinity

This is an eco-friendly way to raise the pH level in your reef tank by limiting CO2 while not raising alkalinity. No need to buy media!

If you grow a refugium properly with macroalgae (chaetomorpha, for example), they will quickly “eat” excess CO2 from the water.

By adjusting the light photoperiod and intensity, you can adjust the growth level.

How To Raise pH In Reef Tank Without Raising Alkalinity

This method, in other words, is wonderful for people who are on a tight budget and prefer putting some more effort than spending money.

Another reason making me really like to grow a refugium with macroalgae is they can eliminate phosphates and nitrates while competing with annoying algae in a reef tank.


Above are some common ways to raise pH in a reef tank without raising alkalinity that I and other experts have found out after years’ keeping corals. We both hope that through this article, you’ll get a better idea of how to fix the vast majority raise in pH of your marine tank.

Thanks for reading!

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