What Is The Ideal Salinity For A Reef Tank?

A reef tank is a saltwater aquarium for live corals, marine plants, and fish. If you are willing to make a reef tank or reef aquarium, you need a good amount of knowledge about salinity. To make sure, good health of your corals, you must maintain salinity with ocean water.

But it is not easy to measure or maintain this stuff without having proper knowledge. In this article, you are about to know the ideal salinity for a reef tank.

What Does Salinity Mean For Reef Tank?

Salinity means the amount of sodium in the water. Since reef tank is made for ocean corals and coral-friendly fishes, the water should be the same as the ocean. It means normal water needs a perfect salt concentration that goes almost identical to ocean water. As a result, your reef tank can be ideal for ocean creatures.

It measures by part per thousand. That means salt part thousand. Experts measure that by measuring the gravity of saltwater and freshwater, then compare them to get the reading.

What Is The Ideal Salinity For Reef Tank?

Ideal salinity is always a debatable question.

However, it would be best if you kept relevant with seawater salinity. But, what is that? Holding it between 1.024 to 1.026 is the most popular salinity level for reef tanks. And considered as safe for corals. Most of the time, it is 1.024. Or at least most hobbyists keep salinity at that level. But, always keeping the natural salinity is the best option for you. Because saltwater fish and corals are used to live in that habituate.

How To Measure Salinity Of A Reef Tank?

There are two types of machines to measure salinity. You can do that with a hydrometer. But, it is not ideal for an accurate result. On the other hand, having a Refractometer can do the job best with accuracy. So, I will talk about how to measure the salinity of a reef tank with a Refractometer.

Salinity measurement using a refractometer

A refractometer is a hollow tube, and it measures salinity via the bending of light through the water. So, take sample water and place that on the glass of the refractometer tube. Then take it close to a light source. You will see the light is bending due to water density. Based on that, it will show a result in a scale inside the tube.

On the other hand, if you have a digital refractometer, it will display the result on a digital display. So you don’t need to depend on your eye reading value.

Every time, you must remember to rinse the slide with fresh water to recalibrate and get an accurate result next time.

How Often Should You Measure Salinity Of A Reef Tank?

You have to check salinity before, and after changing the water, that’s for sure. Due to evaporation, it will change over time. Unless you have an automatic water top-off system, it will increase at an excessive level. So, you have to check it at least twice a week to keep it on a safe level. That will ensure proper health care of your corals.

If you add new fish or corals in your tank, that may change the reading. It would be good to check the salinity level before and after adding fish or corals. However, you may need to add water according to the number of creatures.

Is It Important To Maintain Salinity Level In A Reef Tank?

The reef tank is for saltwater fish and corals. These creatures used to live in the water with a standard concentration level of salt. They can not live in freshwater. Water should be somewhere closer to the ocean salinity level. Otherwise, these fish and corals will not live by any chance.

Saltwater fish and corals are usually live in different temperatures and salinity levels compared to freshwater fish. Because the concentration of salt, water gravity, and oxygen level are also other, these creatures can not take the stress of different oxygen levels and temperatures. And often found dead.

An equivalent salinity level will ensure perfect temperature, oxygen level, and gravity standard for their living.

How To Keep Salinity Ideal In A Reef Tank?

Due to evaporation, you need to care for your reef tank to keep salinity at the ideal level for your saltwater fish and corals. Following things will ensure to keep salinity ideal in a reef tank.

  • Alway pour freshwater to maintain salinity level. In that case, use the automated top-off to maintain salinity level.
  • Make sure that it matches your tank saltwater salinity level whenever you make saltwater. To do that, measure tank salinity, create new saltwater measures and make changes if required.
  • Also, you need to add saltwater if you add new fish or corals to the tank.
  • Above all, check twice a week to maintain salinity. If you see any changes, then react according to that.

Keeping salinity ideal is not tough at all. Yet, evaporation of water makes it difficult. Based on how fast it happens, you have to react. Add water to make it on the level again. Too much salt or less salt is not ideal at all. But, your sea creatures can take that stress for a short period. That is why you have to check salinity levels frequently. And that will ensure healthy living fish and corals to make your reef tank beautiful.


Reef tank salinity is crucial for sea creatures going to live there. Any abnormal changes with seawater may lead to death for your saltwater fishes and corals. So, keeping that at an ideal level shouldn’t take too much time for you. But, you must take reasonable care and check it regularly to ensure the perfect water salinity level. Your marine fish and corals live in a suitable environment where they used to live.