Setting Up a Reef Tank
Part 5

by Marty Ziegler
First published in Gravel Gossip, Diamond State Aquarium Society
Aquarticles

THE CORALS - Mushroom Anemones

Now is the time to add some animals that make your tank look like a living reef. In this article, we'll start with the corals. But first, let's get into a little coral biology, but not too deep.

Coral falls into the Phylum Cnidaria (Coelenterata) with the sea anemones and jellyfish. This is further broken down into the Class Anthozoa, which includes the hard and soft corals, sea anemones, sea pens, mushroom polyps, mushroom anemones, etc. Coral is basically broken down into hard corals and soft corals. The hard corals have a hard exoskeleton while the soft corals do not, although some soft corals appear to be fairly rigid around their base.

We are going to start with the easiest of the corals to keep, the mushroom or disc anemone, which is under the Subclass Zoantharia, Order Corallimorpharia. The mushroom anemones are not true 'anemones' or 'corals', they sort of fall between the two. There are four families, Sideractidae, Corallimorphidae, Ricordeidae, and Discosomatidae. Most of the ones we see are in the latter two families.

Mushroom anemones come in a wide variety of colors, shapes, and patterns. You could almost stock an entire reef tank with these and have more than enough variety. Generally, you will find them at your local fish store on a rock with anywhere from two or three to more than a dozen mushrooms. I currently have over a dozen variations of color and patterns of species to mix and match. They attach at their base to the rocks or the substrate and generally keep a low profile, although they can extend up several inches on their stalk, like a mushroom.

Most of the small, smooth mushrooms belong to the genus Discosoma. Some of these may have small bumps or pimples over the disc surface. Those with bubble-like tentacles covering their entire disc are from the genus Ricordea. The mushroom anemones from both of these genera range in size from one to three inches in diameter, although I have seen these get as large as five inches across. The genus Rhodactis contains the hairy mushrooms as they are covered with hair-like tentacles all over the entire disc, and range in size from two to five inches in diameter. They can swell up quite a bit with water. The largest mushroom anemones are from the genus Amplexidiscus, which have small tentacles spread out over their discs, and can reach a diameter of up to twelve inches. These are known as 'elephant ears' and are known to 'eat' fish! This is one mushroom anemone I would not recommend. I have one and have not been able to keep any gobies or blennies in the same tank, as they will eventually meet their fate as food for these large mushrooms, due to their habit of 'resting' on corals. Elephant ear mushroom anemones have a potent sting, which stuns the fish, and then they just roll up around it, trapping the fish so they can slowly digest it.

Since mushroom anemones have photosynthetic zooanthellae algae, they will need to be placed where they will get plenty of light. Metal halides, power compacts, VHO, HO, or several standard output fluorescent daylight and actinic tubes will all work for providing the minimum lighting requirements for the mushroom anemones. As far as intensity goes, they seem to do fine with moderate lighting, and can be placed on the substrate or among the rockwork. You may have to experiment a little as to placement, depending on the lighting you are using. They also do not like strong water currents. If the current is too strong, they will shrivel up and fall off the rock.

One thing I like about mushroom anemones is that they can be mixed and mingled with other varieties of mushroom anemones and you don't have to worry about most of them stinging or killing their neighbors, like some soft and hard corals can do. The majority of them can be kept in close proximity or can even touch other mushroom anemones and most other reef inhabitants. They propagate by moving along a rock, sometimes leaving a piece behind, to turn into a new mushroom anemone, which is known as pedal laceration. Another form of reproduction is through budding. I have placed a small rock next to the mushroom anemone rock so a couple of mushrooms could 'jump' over to it. I'd move this newly inhabited mushroom rock around to the different varieties of mushroom rocks until I had an assortment of colors and patterns on the one rock. You can also propagate them by slicing in half with a sharp knife or razor blade. Each half will develop into a new mushroom anemone.

Occasionally, one will jump off the rock and fall to the substrate, where it may take up residence. You can carefully move these to a different location, as long as you place them in a depression in a rock or substrate where the water current is not too strong. Otherwise, they will be blown back out into the water column.

Most mushroom anemones can be fed baby or adult brine shrimp, invertebrate food, or finely chopped seafood, but it is not necessary for the ones with zooanthellae algae, as they will derive most of their nutrition from photosynthesis. It is a good idea to use an iodine additive weekly to your tank, as this is essential to the mushroom anemones growth. Although there is usually iodine additive in your salt mix, it can be depleted quite rapidly, within a few days, with a moderately stocked aquarium and a properly sized protein skimmer. Again, the available varieties seem almost endless. They are very hardy, require only moderate lighting, do not require manual feeding, and grow and reproduce easily in a properly maintained reef aquarium.

This will be the last article until September. At that time, we will look at some other easy to keep corals from the Subclass Zoantharia, such as the mushroom polyps. Until then, happy reefkeeping!