What Is The Ideal Alkalinity For Reef Tank?

Alkalinity is one of the most crucial parameters for a reef tank or any other saltwater aquarium. From the health of coral to the performance of aquarium equipment, most of the intrinsic properties of a reef tank thoroughly depends on the level of alkalinity.  

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So if you want to maintain the equilibrium of your reef tank’s alkalinity, you have to know beforehand what the ideal alkalinity for the reef tank is, how to determine it, and what measures you can take to balance it. 

In this article you will get all of these answers, including more information about the alkalinity of a reef tank, which will help you to know your reef tank’s alkalinity better. Additionally, you will be able to improve the alkalinity condition of your saltwater tank in an effective manner. 

Without any more delay, let’s get started.

What Does Alkalinity Mean For Reef Tank?

The term “alkalinity” for reef tanks is used to indicate the total base compound present in a water tank. In other words, it can be defined as the buffering capacity or tendency to resist any change in the pH level. The amount unit is milligrams per liter (mg/L) or parts per million (ppm) of the base. 

Here the most familiar base is carbonate and the amount is referred to as the amount of calcium carbonate. Moreover, reef tankers may refer to the alkalinity as dKH which means degrees of carbon hardness. The amount per dKH is similar to 17.9 mg/L or 17.9 ppm.

What Is The Ideal Alkalinity For Reef Tank?

The ideal alkalinity of a reef tank is 7/8 to 12 dKH. Some aquarists consider 7dKH and some support 8dKH as the least level of alkalinity. Whichever the amount is, it’s correct to follow. This certain level of alkalinity is similar to the alkalinity of the typical ocean surface. 

It is best to create a realistic environment for the reef to grow in a natural manner. In addition, attaining and maintaining this particular alkalinity level will increase the reef’s extra skeletal growth. This optimal level is also important for the independent ecosystem.

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How To Measure The Alkalinity Of A Reef Tank?

The best and most accurate way to measure the alkalinity of a reef tank is by using an alkalinity test kit, like the Hanna marine alkalinity checker. Moreover, using a kit is easy and convenient as well. Here you go through the step-by-step process of checking the reef tank’s alkalinity. 


  • Take the meter and press the “on” button. Wait for seconds until it shows the ready to go status. In Hanna checker it will show up as “add c1”. 
  • Get an optically clear glass holder or container with a fixed cap. Clean it to remove any excess materials like water or cleaning particles. 
  • Now pour a 10ml sample solution into the container and fasten the cap immediately. Fastening the lid is important; otherwise, it can significantly affect the reading. Wipe any excess materials off. 
  • With closed lids, enter the container into the checker and turn on the device. 
  • When the check-kit shows “add c2”, using a syringe, add 1 mL of reagent solution that comes with the check-kit. 
  • Now close the lid and shuffle well to mix the solution properly. Again, wipe out any excess and place the container into the checker and press the button. 
  • The kit will show the alkalinity level in dKH or ppm depending on the format of the kit you have gotten. 

How Often Should You Measure Alkalinity Of A Reef Tank? 

Alkalinity can change suddenly before you notice anything unusual. As a result, regular checks are required to avoid fluctuations in the pH level of the tank. At least once a week, you should check the alkalinity level of your reef tank. However, the ideal is to check twice a week. 

Is It Important To Maintain The Alkalinity Level In A Reef Tank? 

Maintaining the alkalinity level of the reef tank is vital for the betterment of the tank’s inhabitants. The alkalinity of a reef tank maintains the buffering properties of the water. It controls any abrupt pH fluctuations. 

Most importantly, reefs utilize carbonates for their skeleton formation. So, a lack of alkalinity will drastically slow the growth process. On the other hand, a rise in alkalinity is harmful to the devices you are using inside the reef tank. It will initiate limestone formation on the tank wall, surface, and even inside the pump and heaters. As a result, the water flow will be slowed down, and the temperature balance will be affected.

That’s why balancing the alkalinity level and maintaining it is important. Check if the level is at an optimum state. And keep up with routine inspections. 

How To Keep Alkalinity Ideal In A Reef Tank? 

Regular inspection is the first consideration in maintaining ideal alkalinity in a reef tank. If the level of alkalinity drops, add simple lime water or sodium bicarbonate (baking soda) to increase the alkalinity level. The suggested amount is 1 teaspoon of baking soda per 10 gallons of water.

And if the alkalinity level is higher than the normal state, then add a mild organic acid like vinegar. The indication will be 1 mL per gallon in the area of water flow.  

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However, if you notice any severe changes in the alkalinity, it’s best to change the water immediately. For a better outcome, change the water twice every month and give the tank a good cleaning.


Hard work is needed to build a reef tank and maintain its harmony. But with sincere effort, you can enjoy the satisfactory feelings of creating something. There is no doubt how much alkalinity is important for a reef tank. Now you know the ideal alkalinity for reef tanks and every other perk related to it. Check regularly, maintain the level, and repeat. Do not leave your saltwater tank unattended for long periods of time. We wish you the best for your aquaristic effort! 


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