When it comes to calcium level, both high and low calcium can affect the reef tank negatively. The ideal calcium level in a reef tank should be between 380-450 ppm.  So, what if the calcium in your tank goes beyond 450? How do you lower the calcium level in your reef tank?

There are three options you can try to lower calcium in reef tanks. First, just wait for a few weeks to see if the calcium lowers by itself. Second, stop using calcium supplements. Just keep going with alkalinity and magnesium. And third, change the water.

Though low calcium issues are more common, some reef aquarists might face high calcium levels in their tanks. Are you one of them? If yes, this post is written exclusively for you.

In this article, I am going to tell you the bad effects of high calcium in the aquarium along with explaining how to lower calcium in reef tanks. Keep reading.

Why Does Reef Tank Require Calcium?

Before anything else, it is important to know why your reef tank requires calcium.

The corals of your tank depend on the supply of the calcium to grow and flourish. They absorb calcium from the water. Reef tanks need much calcium by the passage of time for better coral coloration and growth. The more corals you have, the more calcium your tank will require.

However, it does not mean that higher calcium levels than the parameter will help the corals thrive. Everything should have a balance in the reef tank for healthy aquatic life. If you do not keep the right balance in the calcium level in the tank, the water chemistry will have negative consequences.

How to lower calcium in reef tank

Effects of Too Much Calcium

Excessive precipitation of calcium carbonate is the result of high calcium. Too much calcium can be bad for heaters and pumps.

When the calcium level exceeds 500 ppm, the alkalinity level might drop. It is because the alkalinity and calcium have such a correlation that one drops while the other increases. The alkalinity level in a reef tank should be ranging from 7 dKH to 11 dKH in a reef tank.

If the alkalinity level drops below 7 dKH, it affects the buffering capacity of the tank water.  And at the absence of adequate buffering, the PH level may start to fluctuate.

However, it does not mean that you will let the alkalinity level go too high. This is also not ideal for any reef tank as it also causes pH fluctuations along with decreasing calcium level drastically that’s not good for corals.

Another important thing to remember is that saltwater fishes and invertebrates are different from freshwater fishes. It is because they are unable to cope easily outside the ideal situation.

An excess amount of calcium changes the other values of the water, creates an imbalance in the water chemistry, and ultimately destroys the perfect aquatic balance.

High calcium stresses the fish and invertebrates. You might see symptoms like erratic swimming, lethargy, and low growth in fishes. And in some extreme and rare cases, too much calcium kills the organisms of the tank.

How to Test Calcium in a Reef Tank?

You should check the calcium and alkalinity level of your reef tank at least once every two weeks. If you can afford it and have the time, I will recommend you check these once a week. It is to make sure that the alkalinity and calcium are not out of their ideal range.

You might be wondering why you should conduct an alkalinity test with the calcium test. Well, calcium and alkalinity have a close relationship where the amount of one affects the other significantly.

When it comes to the test kits, I would suggest you buy a reliable kit from any trusted and reputed manufacturer. The Seachem Reef Status Calcium test kit can help you check the calcium level. You can also try the Hanna Calcium test kit for your reef tank.

3 Ways to Lower Calcium in Reef Tank

Though there are many ways to boost calcium in the reef tank, lowering the calcium level in the reef tank water is quite difficult. There are not many options available to try except the three we are going to discuss.

You can use one option at a time and see if the condition improves. If one option does not work, try applying the next options. In short, keep no stone unturned to see what gives you the best result.

  1. Wait for a Few Weeks

Do not rush to lower the calcium level when the calcium level gets higher a little bit. If the calcium level does not exceed 550 ppm, you should probably do nothing for a few weeks. Just see if the level keeps increasing and staying for a longer period.

Calcium and alkalinity levels can fluctuate in the reef tank for a variety of reasons. It is not necessary to take immediate action to solve the issue overnight.

Just wait and leave the reef tank alone. If there is nothing serious that is skyrocketing the calcium, you can expect that the calcium level will drop on its own. So, nothing other than patience is the first key to lower the calcium in the reef tank.

  1. Stop Using Calcium (in the 2 part dosing)

If waiting for a few weeks has not changed the scenario and you still experience higher levels of calcium in the reef tank, you should apply this second method we are going to discuss here.

This solution might sound bizarre to you. But, it has helped many reef aquarists to handle higher calcium in their tanks.

You might have used the alkaline supplements and calcium supplements in the tank equally when the reef tank was stable and normal. But, now that the calcium level in your reef tank is high, you can simply skip adding a few doses of calcium in the tank water. What you will just use is the alk part, instead of 2-part doses of alk and calcium.

When you do so, the corals will consume the excess calcium existing in the water and thus bring a balance in the water chemistry.

Another reason why this method works is that when you only use the alkaline supplement alone, the water alkalinity increases. And when the alkalinity in the water increases, calcium level drops significantly. It is how the inter-relationship between calcium and alkalinity works. Simple math, right?

So, how long should you continue skipping the calcium and adding alk only? The answer to this question is: keep the calcium supplements off as long as you do not reach the desired target or normal range (380-450) of calcium in the reef tank.

As soon as you reach 450 ppm or lower level of calcium, you should start dosing the alkaline and calcium parts equally and simultaneously once again.

  1. Change the Tank Water

If overdosing is the reason for high calcium, changing the reef tank water can come to your help to lower the calcium. However, you should follow this approach as the last resort when no other options work well.

You can change 25% of the water each week. But, if your tank is 220 gallons or more and it seems that costly for you, you should change about 10%-15% of water per week. It is good if you can run a lower to normal ppm salt mix like Instant Ocean Salt Mix.

If you are lucky and the calcium has not exceeded much, you can start to see the change after a few weeks. However, you are supposed to get the best result after 1 month or more.

Apart from putting effort to lower the calcium down, you have to try to keep the phosphate level in check. Do not let it be more than the parameter. However, if you change the water weekly from 10%-25%, the phosphate level will remain stable too.

Frequently Asked Questions

What is the required amount of calcium range for my reef tank?

The ideal amount of calcium for your reef tank is 380 ppm to 450 ppm. However, it can be as high as 550 sometimes and may come down to normal soon. Give enough time before you move to take any action to lower the calcium level. Keep in mind that fluctuations in the calcium level are common in a reef tank.

What is the ideal alkalinity level in a reef tank?

The least alkalinity level in the reef tank should be 7 dKH and the highest should be 11 dKH. Make sure that you maintain both the alkalinity level without letting it go too up or down. It will affect the overall water chemistry.

What is the relationship between calcium and alkalinity levels?

Calcium and alkalinity levels are interdependent. The basic rule of thumb is when one goes up, the other goes down. For example, when the alkalinity level is high, the calcium level will likely drop significantly in the water.

Final Thoughts

I hope that you have understood how to lower calcium in reef tanks from the discussion above. Make sure that you adopt the approaches one by one and find out the best one for you.

Yes, it might take time, but you have no options left without being patient and keep trying to normalize the calcium in the reef tank by following several methods.

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