Today I'll be taking a closer look at what is still a poorly-understood group of aquarium animals: the anemones. As a hobbyist, I'm consistently surprised at the lack of good information available on these popular marine aquarium creatures and the prevalence of not-so-accurate "aquarium lore" regarding anemones that despite not being factually based still comes up surprisingly often in the literature. With that said, let's take a look into this fascinating family of cnidarians.
|The Haitian Pink Tip or Condylactis anemone (Condylactis giganteus). All purple color form, left|
Care and Handling:
One of the most frequent issues experienced with anemones in captivity (and probably one of the reasons they have retained a reputation for being difficult to keep) is improper handling, either when collected, at a wholesale facility, or at a local shop. Anemones anchor themselves to the seafloor using an adhesive "foot" called a basal disc, and ensuring that this disc does not get damaged throughout the chain of custody is crucial to any anemone's long term health. The basal disc is easily torn or damaged, and because of this we keep all anemones in soft mesh baskets to ensure that they have a rugged surface to adhere to but one that makes it easy for staff to gently remove them as they get shipped out. Keeping anemones in empty glass or acrylic tanks encourages them to cling to the sheer sides and can make it extremely difficult to safely remove them. Worse yet, anemones housed in aquariums with any rock or similar structures will be nearly impossible to remove without damage. Keeping them in a tank with a mixed-grade aragonite substrate and some rock rubble is fine and can actually facilitate removal, especially in a retail setting.
|Our anemone baskets in use and full of healthy Condylactis enjoying the mid-day sun|
A healthy anemone will be firmly attached to a surface, with a base that doesn't show discoloration or any unusual protrusions. Having fully extended tentacles is a good sign, but be aware that anemones naturally retract and sometimes close up entirely throughout the day; this is not necessarily a bad sign. Perhaps the most important cue to look for, aside from ensuring the disc is not damaged, is coloration. An anemone that is exposed to stessors, particularly high temperatures, is likely to "bleach out" just like corals are known to do. Bleaching means that the anemone expels the symbiotic algae cells in its tentacles. These algae cells are what give the anemone's tissues a brownish or greenish coloration so a bleached anemone is usually, as the name implies, bright white.
|Healthy Sebae Anemones. Note the brownish tint to the tentacles|
Some species, especially carpet anemones, are normally a bright fluorescent color and after experiencing bleaching will look neon, almost more vibrant than before. Beware of anemones that look unnaturally colorful or bright, as it is often a sign of advanced bleaching. In these individuals, the tentacles and tissues often appear translucent. While bleaching in no way means an anemone is doomed, it requires skill and patience to care for a badly bleached out specimen. Because the anemone will have lost its ability to take in nutrients from sunlight, it will need to be fed heavily and protected from overly bright light during this time.
|Although it may appear to be a vivid neon green, this is just a badly bleached |
specimen. Notice the translucent tentacles and body
Perhaps one of the most important and frequently overlooked aspects of anemone care, especially once it has been introduced to the home aquarium, is feeding. Many people assume that, like many corals, anemones mainly rely on lighting for nutrition. It is important to remember that anemones are carnivores, and despite being opportunistic feeders, can be quite predatory if given the chance. I've found that anemones will thrive on twice-weekly feedings of chopped shrimp, krill, smelt, or other meaty food items. For smaller specimens I use frozen mysis and finely-chopped shrimp. Each anemone will have different feeding preference and you will quickly discover which foods are their "favorites" by which food particles adhere to their tentacles best.
To conclude, anemones are one of the most fascinating groups of cnidarians in the sea. Despite having been kept in aquaria for decades now, there is still a lack of solid husbandry guidelines available to the average hobbyist, which unfortunately perpetuates the myth that they are all difficult to keep. Many of the commonly available species make excellent additions to a reef or fish only aquarium when well cared for and may even reproduce in aquaria if conditions are right.