Anemones have many of the requirements that corals have: adequate light in the right spectrum, good water movement, proper nutrient levels, adequate trace element levels and a stable salinity. Aquarists who aspire to add an anemone to their aquarium would be well advised to invest the resources and time required to develop a high quality reef tank system before purchasing an anemone.
Anemones live in warm water (80+) in the wild (Indo-Pacific, Red Sea areas). Keeping your aquarium at a stable temperature between 80 and 85 degrees will help reduce zooxanthallae stress.
Lighting requirements are the same as for hard (LPS/SPS) corals, which would be metal halide or its Power Compact equivalent at a rate of 4+ watts per gallon of tank water in a 16" deep tank. More, for deeper tanks.
Trace element levels should be kept high, regularly using a supplement.
Regular dosing with phytoplankton and/or zooplankton.
Anemone Foods & Feeding
Anemones shrink by consuming their own flesh in times of famine, or grow (swell) when well fed.
Symbiotic algae (zooxanthellae) reside within the anemone's tissues and provide them with nutrition via photosynthesis, hence their requirement for high intensity light in the right spectrums.
Anemones derive nutrition from absorbing nutrients directly from the water.
An anemone's nemocysts can sting prey (fish, urchins, snails, small crabs), which is then moved to the mouth with their tentacles. Anemones can also consume the wastes of resident animals (Clownfish).
Anemones are protein specific, accepting some sea life for food and rejecting others. Experiment with a variety of foods to find which ones your anemone will accept. Captive hardiness seems to be related to the availability of a variety of foods.
In the wild, anemones live in the nutrient rich "soup of the ocean". Anemones derive nutrition directly from the water they are in, so keep in mind that protein skimmers remove anemone food from the aquarium water.
Anemones seem to position themselves for maximum current, presumably to better collect plankton. Perhaps this is why they seem to head for pump intakes, where they are damaged or destroyed.
Anemones & Clownfish
How can Clownfish live in anemones?
A Clownfish that has lived without an anemone for a period of time can lose its protection. Without going into a long scientific explanation, just understand that clownfish create a mucus which protects it from the poisonous nemocysts that anemones fire from their tentacles. These nemocycsts are used for defense from predation and for disabling a prey for consumption. When a clownfish is introduced to an anemone, it may take hours or days for the fish to build up its protective mucus.
An interesting note: Brooks and Mariscal (1984) found that Clark's Clownfish which had been acclimated to synthetic anemones (rubber bands imbedded in silicone) were able to acclimate to real anemones 8 times faster than similar specimens that had been kept without anemones (real or synthetic).
Observations and conclusions from the above mentioned survey:
Lighting: 3.5 to 4.3 watts of high intensity aquarium light per gallon of aquarium water with half of it coming from actinic blue lights. Photo period of from 12 to 13 hours per day was best. Entacmaea quadricolor was the apparent exception, surviving and even cloning under regular output fluorescent lighting (these tanks had a high fish population, current and zooplankton level).
Specific Gravity: Anemones need an SG of 1.024 to 1.025. Anemones are not osmoregulators, they are osmoconformers which must reach equilibrium with their surrounding water.
Anemones can not regulate or store trace minerals in their tissues, so they must be constantly maintained at the right concentrations. In the study, the anemones of the hobbyists who used tap water (as opposed to RO or highly purified water) fared much better. The reason may be the higher trace minerals (which anemones require) contained in tap water. The anemones in nutrient rich water fared better than in nutrient poor water. Since protein skimmers remove nutrients, their use may not be advised.
Anemones need water current to remove debris from their surface and to bring them nutrients (i.e. plankton). Without adequate current, mucus can build up on the anemone's surface, this can inhibit respiration and attract bacteria which feed on mucus.
Host anemones should be at least 3 times larger than the Clownfish which are to reside in it. A Clownfish (or 2) which is too large for the anemone can damage the anemone when it tries to burrow down into its tentacles.
Now that you understand all of the challenges ahead if you elect to take on putting an anemone in your aquarium, prepare your tank to give the anemone the best chance it can have to survive. Before you buy an anemone, read the Anemone and Clownfish profiles to make sure that your match up will work. Clownfish are pretty selective when it comes to choosing its host anemone.