Why Is My Anemone Closed? Check The Conditions Of Its Life

Why Is My Anemone Closed? Check The Conditions Of Its Life

“Why is my pet anemone closed?” is a usual question that might bother an aquarist, especially if the anemone has been closed for up to a week or more.

We are going to shed light on this topic. At the end of this post, you will know the reasons that give cause for alarm and those that don’t when you notice that your anemone is closed. You will also be better informed about routine practices that protect and maintain the health and habitat of your anemone. Let’s get started!

About Anemones 

Anemones are colorful and beautiful invertebrates that are usually found in coral reefs. Although they are mostly found in the wild, many aquarists have imbibed the culture of keeping anemones as pets in water tanks. These water tanks are designed to imitate the atmosphere of their natural saltwater habitat.

Although anemones are also prey to some marine life such as sea slugs, starfish, sea turtles, and some others, their tentacles are venomous, and they use it to stun preys that come within their reach. Depending on the species, adult anemones can grow as long as 4 to 48 inches across.

These beautiful reef invertebrates come in striking colors and require moderate to strong water movement in the tank. It would help if you also had a feeding routine to feed them at regular intervals. They pair well with a few other photosynthetic marine life and depend on a symbiotic relationship with alga for energy. Other marine organisms they pair well with include clownfish, anemone crabs, etc. 

They are carnivorous, with their diets mainly consisting of sea urchins, shrimps, amphipods, mussels, planktons, and tiny fishes.

Possible Reasons For the Close Up

Possible Reasons For the Close Up

If you find your anemone has closed up for a while, it may be no cause for alarm. But sometimes, your anemone can close up for more than a month, which could occasion some concern on your part as the owner. 

Reasons for the close-up vary from alarming to habitual ones. Below are some things that could cause your pet anemone to close up.

Food Related Causes


When your anemones are getting too much food to eat, they may close up to prevent more food from getting into them. This is natural. Although it is not much of a cause for alarm, you should watch how frequently you feed them if you are concerned that they are closing up. 

Although this reason is less likely to cause the death of your anemone, too much food may lead to stressing your anemones and altering the habitat aside from the issue of waste.


You may notice your anemone closing up and shrinking even though you observe the regular feeding schedule. This could be caused by starvation. A likely reason your anemone is starving may be the water flow. When the water flow in your aquarium is too high, the nutrients and food are likely to be pulled away from the anemone even before it has got a chance to eat. 


You need to be deliberate and take active steps in helping your sea anemone open up, eat and grow. Doing this may seem challenging because getting food to your closed anemone may be difficult. But one practical method to remedy this situation is to place a container over your anemone and use a turkey baster to get food to it. This way, your sea anemone should respond by opening up again and feeding well. 

Protective Feeding Habit

Sea anemones typically close up when they are feeding. They drag food particles with their tentacles to their mouth and usually close up to feast on the trapped food particles. They do this to protect themselves while eating.

This protective feeding habit is instinctively ingrained because they close to protect their tentacles and internal parts from predators in the wild.

If your anemone stays in the tank alone, it may still practice this protective feeding habit, so there is absolutely no need to worry if you notice your anemone closing up right after you feed them.

An ideal anemone diet usually consists of small amounts of frozen foods such as shrimp (Mysis shrimp or brine shrimp), silversides, or freeze-dry krill. Depending on the size of the sea anemone, you may feed it once or twice a week. If your pet anemone is larger, the feeding routine should be more than twice a week. Remember to defrost frozen food before feeding your pet anemone. There is no need to feed supplements to your anemones, but you can if you feel like it.

Habitat Parameters

Habitat Parameters

If you put your anemone in the tank and it closes up almost immediately, it could be that your tank is not mature enough. The challenge here is that the water in your tank is yet to grow those natural bacteria and imitate the sea habitat for your anemone to acclimatize to. This process usually takes an extended period – from six months to a year. So, you might want to hold off on that impulsive purchase and go for an already mature tank or wait for your tank to mature enough for your anemone.

Anemones require a specific ratio of nutrients and habitat parameters for the maintenance of their health. If the water parameters are off, your anemone will close up to indicate that the nutrients in the water are incorrect for its habitat parameters. 

To prevent your anemone from closing, keep to the feeding routine and ensure that the water in your tank is within the normal parameters. Although some species may have special needs, general needs are common for all species. These are:

  • The water in the tank must be clean and free of debris. 
  • The water temperature must be within the range of 76°F and 82°F.
  • The salinity of the water should remain at a stable specific gravity in the range of 1.023 and 1.025.
  • The nitrate level in the water should not be more than 2 ppm.
  • Levels of phosphate, ammonia, and nitrite should be as close to 0 as possible.
  • The water pH should be stable and in the range of 8.1 to 8.3, i.e., the average alkalinity level of saltwater.


Sea anemones sometimes close to change their location, and they do this for some reason. One of these reasons is the flow of water in the tank. Although they are slow when they move, your sea anemone will be open again once it settles in its chosen location. The flow in your tank should be moderate. Check regularly to ensure that the flow is not too strong for your pet anemone.


Lighting may also be the cause of your sea anemone closing up. Just like the flow of water in the tank may make it close up to switch locations in the tank for an ideal spot with the ideal or manageable flow, too much or too little lighting can also make your anemone close up.

Anemones usually close up at night to conserve energy and hide from potential predators. If it is the case that the light is low and your anemone is closed, it is likely to close up to rest, so you shouldn’t be alarmed.

Also, anemones and corals have a symbiotic relationship with an alga called zooxanthellae which gives the anemone energy in exchange for nitrogen and carbon. For this symbiotic relationship to continue undisturbed, anemones require power lighting to cater to the needs of their algal symbiotes.

How do I measure the lighting?

Photosynthetic marine life requires no less than 5 watts per gallon as the usual lighting rule. But there is no hard and fast rule to it. Deeper tanks need more powerful lighting. 

If you are using LED lights, you cannot go with the five watts per gallon rule because it is better to measure the output of LEDs in Photosynthetic Active Radiation (PAR). Usually, manufacturers of LED lights for tanks have a chart for measuring the amount of light that is ideal for your tank, and it is usually included in the arrays you purchase.

How long do anemones close up for?

Sea anemones can close up for an extended period. They can close up for as long as six months in extreme cases before opening up again. So if your anemone closes up for a long time, do not panic. Be sure to check for any of the reasons listed above before thinking the worst.

Final Thoughts

Pet anemones are lovely creatures. Although many aquarists keep anemones as a hobby, there is no doubt that it adds color and style to the room where it is kept. Apart from giving your room a sophisticated taste, they also give you a chance to be closer to nature and study marine life’s beauty. So when your anemone closes up next time, check these likely causes described above, and you’ll find the problem that needs fixing.