Why is My Sea Anemone Closed?

If you notice that your sea anemone is closed or closes for long periods of time, don’t freak out. Before you panic and think that your anemone is dying, it can be perfectly normal for your anemone to close.

While some of the reasons can be bad, such as starvation, putting your anemone into a tank too early, or incorrect water parameters, sea anemones have been known to close simply because of the time of day or to feed.


If you place your sea anemone into your tank and it closes up, you might wonder, “Why is my sea anemone closed?” Especially if you’ve checked the water levels and done everything right, this question is understandable.

However, one of the biggest reasons that an anemone doesn’t open is that the tank itself isn’t mature enough. You might want to test the water just in case, but a lot of the time a newer aquarist will see a good deal on anemone and purchase it.

The problem there is that it takes time for the water in your tank to develop natural bacteria and acclimation for your sea anemone to accept the new conditions. This can take anywhere from 6 months to a full year, so patience is key when it comes to adding a sea anemone to your tank.

Food Possibilities

If your sea anemone has suddenly closed up, there are 3 possible food-related reasons: Starvation, overfeeding, or they’re eating. While 2 of these are negative, only one can kill your anemone.


It’s not uncommon for your sea anemone to deflate, especially at night, but there’s a noticeable difference between deflation and shrinking. If your sea anemone is distinctly getting smaller, that’s a good sign of starvation. 

This could be because your water flow is too high and is pulling nutrients and food away before it has a chance to eat, or the other inhabitants of your tank, especially clownfish, could be eating its food.

With your sea anemone closed up, it may seem difficult to feed them. One of the easiest methods is to place a container over your anemone and use a turkey baster to get food to your sea anemone. This way, the food can’t be stolen and your sea anemone should grow again.


If they’re getting too much to eat, sea anemones can close up to make sure nothing else gets in. Make sure you monitor how frequently and how much you’re giving your sea anemones and adjust accordingly.

Overfeeding won’t kill your anemone, but it’s a waste of food and can begin to stress your anemone.

They’re Eating

Likewise, a sea anemone can just close because they’re eating. They use their tentacles to drag food to their mouths, at which point some of them close to protect themselves while feeding. 

This is an instinctive mechanism to protect their tentacles and internal parts from predators in the wild. Even without predators in the tank with them, sea anemones can still do this so don’t worry if that’s the case.

Water Parameters

Another thing that won’t kill your sea anemone but can cause it to close up is if the water parameters are off. Your anemone will close as an indicator that the nutrients in the water aren’t correct for its natural life. 

Low amounts of nitrates in the water are acceptable, unless you have corals, but check the calcium, magnesium, salinity, and other nutrient levels in your water. If nothing else, do a water change of 20 to 25 percent of your tank to replenish and restore the levels to normal.


While water flow can cause your sea anemone to close, one of the best things about your anemone is that it’s capable of movement. It may be slow progress, but your anemone will move to an ideal location in your tank.

So, while it may close for a while to move positions it should open up again once it settles in.

Good Night, Anemone

Sea anemones have been known to close during the night just to conserve energy or instinctively hide from potential predators. This isn’t unusual and should give you no cause of alarm.

If they don’t open up the following morning, however, you may want to go down the checklist above because it probably means something went wrong in your tank overnight.


One of the other possible reasons for your sea anemone to close up is the lighting. While this isn’t dangerous to your anemone’s health and the sea anemone, much like with the water flow, will move to a location it prefers, lighting can be too high for your anemone.

Make sure to research what the maximum power level is to have in your tank for all inhabitants, but sea anemones are usually satisfied with low-level LED light strips. Of course, if you have other life in the tank that requires higher lighting you might have a problem.

How Do I Know if My Anemone is Dead?

One outcome that no aquarist wants to consider is that their sea anemone has died, but it’s definitely a possibility with any lifeform in your tank. It could be death simply from a tank that’s just not had time to mature, so watch out for those impulse buys.

It could also, unfortunately, be from stress due to any of the reasons above or the reasons themselves. Either way, if your sea anemone dies the best way to tell is if it’s closed and begins to flake off inside the tank.

When this happens, withdraw your sea anemone from the tank before toxins begin to seep through the rest of the tank and kill the other sea life. The timetable depends entirely on how good your filtration system is, but the sooner the better.

However, make sure that it’s actually dead before doing this because you could kill it by accident. Sea anemones can close for up to 6 months before opening back up in some cases, so you might also want to hold off on dosing your tank with vinegar before checking everything else.


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