pH can be a complex subject, especially for saltwater aquariums. It is essential to not only understand what pH is, but how and when it changes. Having a firm understanding of pH will make it easier to diagnose issues and address them accordingly.
What is pH?
pH is the acidity or basicity of water measured on a scale from 0-14, with 7 being neutral. A pH value below 7 is acidic, and a pH value above 7 is basic.
Why is pH Important?
Keeping the pH in the proper range is essential for coral growth, allowing corals to lay down calcium carbonate skeletons easier than when in lower levels. While short periods of low pH are relatively harmless, prolonged periods of low pH will hinder growth and lead to tank failure. Corals grow best between 8 and 8.4; however, it is common and harmless to have the pH drop as low as 7.8 at night.
What is the Optimal Range?
Freshwater Aquariums: The range for a freshwater tank can run from as low as 6 to as high as 8.5.
Reef Aquariums: The range for a reef tank should fall between 7.8 and 8.4.
Tools for Measuring pH
There are a few different options to choose from when measuring your reef tank’s temperature:
Aquarium Monitor or Controller
A pH monitor and pH controller will both continuously measure and display the pH of the aquarium. Unlike a pH monitor, a pH controller can also send an alarm when the pH falls out of range or turn off equipment that may be causing the pH to drop out of range. For example, a pH controller can turn off a calcium reactor if the tank’s pH is low. This will prevent additional low pH calcium carbonate from being added to the system.
In advanced aquariums, a pH controller can also control the addition of chemicals to increase or decrease the tank’s pH. pH Controllers are generally the most expensive option. However, unlike other options, it allows you to know your aquarium’s pH at a glance and understand if other issues need to be addressed.
Hand-held Tester
Hand-held meters are relatively inexpensive compared to a pH monitor. These can provide results within a matter of seconds. Using the tester is as simple as dipping it in the water and pressing a button.
Test Kit
A chemical test kit utilizes a water sample, reagent and color comparison chart to determine pH. Test kits are generally the most inexpensive option for measuring pH.
The Relationship Between pH and Alkalinity
Often times there is confusion between alkalinity and pH, as well as how they interact with each other. A simple way to think about this is that alkalinity is the aquarium water’s ability to resist pH changes. Generally speaking, the higher the alkalinity, the more stable the pH.
How to Fix Low pH
Traditionally, most folks would add a pH buffer to raise the pH, but this is merely a band-aid treatment and does not adequately address the root problem. Below are the three most common causes of low pH and how to correct them:
1. Low Alkalinity
Check your alkalinity to make sure it is in range. A proper alkalinity level of 8-12 dKh will usually keep pH in the appropriate range. Adequate alkalinity levels are also needed to maintain appropriate calcium carbonate levels, which is the building block of coral structure.
2. Improperly Tuned Calcium Reactor
If you are running a calcium reactor, check your set-up. The calcium carbonate produced by a calcium reactor has a low ph, so too much can cause the pH to drop. Too much CO2 can also cause pH to drop.
3. High Carbon Dioxide Levels
High carbon dioxide levels are the most commonly ignored situation. If alkalinity levels are correct, elevated CO2 levels are the most likely cause of a low pH. It may seem far fetched to think opening a window near your aquarium will fix this issue for you, but it is true. Using fresh air to exchange out the excessive CO2 will increase your pH.
In most tanks, pH drops at night because corals decrease photosynthesis, which consumes CO2 and change to respiration, creating CO2. Corals are animals, after all, and they need to breathe too. One popular method to address this issue is to run the air input for your skimmer outside, drawing in the fresh air. People, pets, cooking, and other activities can dramatically increase CO2 levels inside the home, so pulling air from outside can significantly reduce CO2 levels in the aquarium.
How to Fix High pH
Low carbon dioxide levels are the cause of almost all high pH situations. The same method of drawing fresh, outside air into your skimmer works here as well. The outdoor air will raise carbon dioxide levels back to normal and rarely cause carbon dioxide levels to increase to a level where they can cause the pH to drop too low.
We hope you learned something today about pH, the cause of pH issues, and how to handle them. Be sure and visit Simplicity Aquatics blogs weekly for additional tips, tricks, and more information.