Coral Only Tank

Coral Only Tank? Can You Keep Them?

Coral only tanks are a possibility when you are keeping an aquarium. Corals have slightly different needs to fish, for example, but as long as you feed them and keep the aquarium well maintained, a coral only tank can flourish.

In the rest of the article, we are going to look into whether you can keep coral without fish and have a coral only tank, whether coral only tanks need water changes, and whether corals can survive a cycle.

Can You Have a Coral Only Tank?

Our cultures view aquariums as necessarily housing fish or other lifeforms that are more intuitively animal, but not only is the coral an animal too, but they can also survive in an aquarium without fish. Some people may view this as an inferior aquarium from an aesthetic perspective, but it is no less rewarding and no less alive than a tank with fish.

Corals are natural predators, which means that in the wild, they hunt their prey, which includes microscopic plankton and even tiny fish. While the corals that share an aquarium with fish in a household probably won’t be eating them, it is a misconception that corals subsist entirely off of fish waste. Since this is not true, it stands to reason that corals can survive without fish.

If you have a coral only tank, there are considerations that you will have to keep in mind, but these are not overly different from foundational aquarium care for any marine life. You will need to make sure your corals are fed, and you will need to keep the water in the tank in good condition. If you can do all that, your coral only tank is set.

Do Coral Only Tanks Need Water Changes?

You will still need to perform water changes for coral only tanks. Even though it can be easy to forget it while looking at them, corals are still living creatures, which means that they will also produce waste and change the composition of the surrounding water. Without water changes, these gradual modifications to the water will eventually lead to a very unhealthy environment for your corals.

In spite of the massive range of supplements and filters and other equipment and supplies on the market for aquariums, water changes continue to be a mandatory part of the care process. This is as true for aquariums with corals as it is for aquariums with the fish that would be living around them in the wild.

Water changes are essential to removing the accumulated waste material in your aquarium, which may present a number of hazards, but they will also replenish nutrients that will have been used up over time. In nature, whole ecosystems will perform these functions flawlessly, but in a small, enclosed space like an aquarium, this cannot happen without human intervention.

Because water changes are all about keeping your aquarium’s long term health up to scratch, you won’t necessarily see the problems with not doing it early on. For this reason, do not be tempted to pull water changes out of your routine just because you skipped a few and your coral still looks fine. I can guarantee you that it will not do so for long.

Can You Keep Coral Without Fish?

Although it is common to have aquariums with both corals and fish, in the same way that you can have tanks with fish and no corals, you can also have tanks with corals and no fish. In fact, corals can even thrive in aquariums without fish as long as they are taken care of properly by you.

There is food specially designed to be fed to corals, and this can pick up the slack from the missing fish in your tank. Remember that your corals do need to eat, so you will have to do something to make up for the absence of fish, with coral food being the easiest solution.

Corals can even find a number of advantages to living in an aquarium without fish. For example, they will no longer have to compete with the fish for shared foods that you might be putting into the tank. Furthermore, fish can nip at corals, even if by accident, which can be annoying to them at best. This is no longer a problem without any fish in the tank.

Can Corals Survive a Cycle?

It is not advisable to have corals in your aquarium while it is undergoing a cycle, and definitely not under any circumstances before you have completed the ammonia stage of the nitrogen cycle. Because nitrite is still toxic, and this chemical is plentiful after the end of the ammonia stage, it is still best to hold out on introducing your corals if you can.

The nitrogen cycle goes through three stages. In the first stage, the toxic chemical of ammonia begins to be converted into nitrite. Although corals will not survive with too much ammonia in the water, nitrite does not make for a very healthy living environment either, and you will likely see your corals brown out from it.

While it is true that they will technically survive this stage and the excessive nitrites, you may lose some of them, and this will not set them up for good long term health, which should be the goal of anyone keeping an aquarium.

After the nitrites are converted into nitrates, the nitrogen cycle ends. For best results, wait for your algae to bloom so that you can introduce your corals to a nice little functioning ecosystem. If you would rather not do that, the water is at least safe and non-toxic for your corals after the nitrogen cycle is complete.


We’ve learned about how to look after a coral only tank and that fish are not a necessary part of the ecosystem in a home aquarium where you want coral to thrive. We have also looked at the importance of water changes in coral only tanks and how corals interact with nitrogen cycling in an aquarium.