I am currently undertaking a RBTA propagation project and have noticed that there are several reasons that I observe an anemone shrink. One of those reasons anemones shrink is caused by starvation. While starvation sounds very harsh and easily avoidable I have noticed in a system with dozens of anemones some of the individual anemones will crawl under or behind rocks out of sight, and therefore miss being fed directly. In this article I will discuss how to recognize a starving anemone and how to hopefully bring them back to full health.
If you are reading this article because you are worried that your own anemone is shrinking the first step is recognizing if it is shrinking from normal waste removal or for a different unhealthy reason. Before you begin to worry a healthy anemone will frequently deflate to remove waste from its body and over the course of several hours will inflate to its original size. If your anemone has only been deflated for a few hours then there is probably no cause for alarm. Anemone waste removal is normal and nothing to worry about. However, if the anemone stays deflated over the course of a day or longer this indicates a health issue and I would recommend a large water change and running carbon immediately. I will cover anemone health issues in a later article.
If your anemone is shrinking but it’s not an issue with deflation then one of the likely culprits is starvation. Examples of this are shortened tentacles, bleaching in color, and a shrinking diameter. In my particular case 99% of the anemones in the anemone farm are healthy and thriving, for reasons I have not yet identified certain individual anemones will crawl under a rock away from the light and stay there indefinitely.
In the pictures below you will notice that the anemones in this section of the propagation farm are healthy, large, and thriving. However, just under this rock I found an anemone which was starving to death. Why did this anemone choose to hide in total darkness growing weaker and weaker when the others did not? Unfortunately, I do not yet have an answer for this but I am working on it.
Here you can see the starving anemone. The tentacles have shrunken down into small nubs and the color is almost completely diminished. By this point its tentacles will not catch any food. The only way to feed this poor anemone is to place small pieces of food directly onto the mouth. You must also kill all the current in the tank so that the food doesn’t blow away. When I have an anemone in this state I offer it food daily. In most cases it will not take food every time but slowly over the course of several weeks it will regain its strength, color, and tentacles.
Sadly they do not all make it, but with daily feedings most will be alright. I have seen shrinking anemones in friend’s tanks as well. Regularly fed anemones were still starving. The reason for this was shrimp or fish were stealing the food from the anemones mouth. I have also seen problems with hosting clownfish never allowing the anemone to get a meal. I’m not sure what causes this, but the result is the anemone needs to be separated from the clownfish so it can regain its strength and able to feed on its own.
If you have a starving anemone yourself I hope this article helps you recognize the problem and gives you the information needed to save the animals life.