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Why Your Coral Is Not Opening Up!

After the initial surge in keeping fish a couple of years back, many people who stuck with the fish keeping hobby are now progressing into more advanced tank setups such as reef tanks and adding corals to their setup.

With corals being a challenging addition to a reef tank for an experienced fish keeper, we have noticed many of the people new to keeping corals reaching out to ask for advice on why their coral is not opening up.

Depending on the type of coral you keep, the most common reasons that it will not open up include problems with water parameters, water flow, light intensity, nutrient levels, salinity levels, and tank mates eating or nipping them.

Most of these are very easy to fix and you should be able to diagnose and correct the problem quickly and easily to get your coral to open up and grow at a healthy rate.

We have a dedicated article going over flower pot coral not opening up that we wanted to make you aware of due to flower pot coral being one of the more common corals kept right now with it being a very popular option with it often being a more difficult coral to care for so you need a couple of specific things in place for it to open.

We always recommend that people new to keeping corals try to stick with the more beginner friendly types such as zoanthids with a zoa tank being a great way to rapidly gain experience in coral keeping.

Why Your Coral Is Not Opening Up!

Most people will find that their corals are not opening up due to their tank not having suitable water parameters, water flow or incorrect light intensity for your coral.

Less common problems that many people new to coral keeping can often have problems with also include problems with nutrient levels, salinity, and none reef safe tank mates eating or nipping their corals.

Just like we covered in our article on hammer coral, the most common problem by far is issues with water parameters and this is often not directly the fault of the aquarium keeper but their tools.

So many people start off with a cheap water test strip water tester that is not only inaccurate but also doesn’t test for all water parameters that corals are sensitive to.

We would always recommend that you go with an actual reef tank water test kit that is only a little more expensive than the cheaper kits while being far more accurate and testing for more parameters that can cause issues with your corals letting you maintain your water in a better way to get your corals to open.

Problems with water flow and light intensity are probably the second most common issues that will prevent your corals from opening up but we will cover how to fix this in the section below.

The less common problems for most people are based on issues with nutrient levels because yes, you do have to feed your corals or provide nutrients of some sorts in many tank setups even though many people new to coral keeping realize this.

How Do I Get My Coral To Open Up?

If your coral is not opening up due to problems with light intensity or water flow in your tank then you may have to adjust the location of your coral in your tank to an area with less light and lower water flow.

If you are able to leave your coral in its current location and lower your light intensity and water flow then this should always be your default action but this will depend on what else you have in your tank.

We touched on this next point in our article about toadstool coral but one thing that is becoming more common is that people will add none reef safe fish to their reef tanks.

This used to be very rare but more and more people are going for the unique looks and colors of the fish rather than the safety of their coral and unfortunately, these fish then eat, bite, and nip your coral forcing them to stay closed so try to only go with reef safe fish and shrimp.

Salinity levels can be a problem as different corals require different salinity levels as well as other variables such as water parameters and water temperatures.

This can be a problem for people new to keeping corals that will result in the corals staying closed due to unoptimal conditions but these can be easy to fix.

The problem is that people new to keeping corals can sometimes add a huge range of corals to the same tank that all need very different water conditions making it impossible to balance the tank to get your corals to open so you have to factor this in too.

How Long Does It Take For Coral To Open Up?

Once corals are happy with their water parameters they will usually open up within a couple of days but it can sometimes take as long as a month.

In rare situations, usually when your coral has stayed closed due to being eaten alive by a tank mate, the coral may take months to open up with slow progress being seen with each month that passes.

As we mentioned in our article on candy cane corals, this is totally normal and most people should expect a wider time frame for their corals to open once the problems have been corrected rather than a narrow, specific number of days.

This is due to corals being sensitive and even the beginner friendly corals can be a challenge to care for but most people will often find that they will be fine and open up within a month.

When you move on to keeping intermediate and expert level corals this changes completely though as they can be ultra sensitive and we usually don’t recommend you even try an intermediate coral until you have three years experience of keeping beginner friendly corals.

Some of the expert corals that can be super sensitive can take years to open after having problems with their water parameters.


That brings our article going over why your coral is not opening up and how to fix it to an end. We hope that we have been able to help you better understand the more common problems that you should be looking for if you are having problems with your corals not opening. For the most part, the more common issues do tend to be very easy to correct though and the majority of our readers should be able to fix the problems with minimal issue in the long term.