Sea Mat: An Ocean Of Color For The Aquarium

by Blane Perun

My name is Blane Perun, the creator of thesea.org. I have been somewhat obsessed with collecting Sea mat for nearly 3 years now, since my first introduction to these species. Building an impressive reef ecosystem consists of not only providing for the health of the tank inhabitants, but functionality and aesthetics as well. I have found the Sea Mat to be great addition for providing that perfect supplement of color when creating your reef scene. I have often referred to my display tanks as underwater gardens, and as the reef is to the garden, the Zoanthus (Sea Mat) is to the flower that lies within. Prior to working with these polyps, creating contrast in texture and color was, in some cases, very difficult. With an SPS-dominated tank, I often found myself with too much blue or too much green. Once I stumbled upon these creatures, the barriers of balance were tamed and the possibilities were endless.

Taxonomy

Technically, Sea Mat is just a common name, as are button polyps, colonial anemones, polyp rock, and false coral- all primarily referring to Zoanthus. All of the Genus in this piece are part of the family Zoanthidae within the subclass Zoantharia in the class Anthozoa. Some of the members in the genus include Palythoa, Protopalythoa, Zoanthus, and Isaurus, amongst others. Wilkens (1990) described some 300 individual species. However, there looks to be less than a fifth of this, realistically. (Borneman 1997) notes that an overhaul is coming in which we will see a reclassification of species, and in some cases, the entire genus.

Physical Characteristics

To some extent, the physical characteristics of the colony are influenced by it’s habitat of origin. Two identical colonies could appear somewhat different, just like we see in other corals. Shorter, more compact specimens with smaller mouths for the most part come from high current areas. The specimens with more

elongated bodies, larger mouths, and longer tentacles more likely come from low current areas. Interestingly, these species occur in nature in a myriad of conditions from one extreme to another. Zoanthus colonies have been observed from reef crest (taking blows from the crashing waves) to tidal areas (being exposed to air for hours during low tide). In fact, it’s the durability of the species that make it such a good choice for the aquarium. These polyps tolerate a wide range of conditions and will flourish in nearly any aquaria.

Zoanthus have smaller polyps and reproduce by forming buds from the base of the mated tissue. This species, unlike some of the others in the family, does not incorporate sediment into its base. The oral disk is in the center of tightly-packed tentacles, and appears in nature in a variety of colors and endless combinations.

Palythoa have larger polyps but are also embedded in a common tissue. The texture of the base of both the Palythoa and Protopalythoa is rough from the incorporation of sand and sediment directly in the tissue. The assimilation of the material is thought to be both for defense and support. The larger polyps lend themselves to feeding on larger meatier foods.

Protopalythoa  are much like the Palythoa in size but with the exception that the polyps are not connected to one mass of tissue. Some seem to have less more pointed tentacles in some cases they even alternate up and down (Sprung 2001)        

Selecting Stock & finding a gem

It is important to remember the Zoanthus have symbiotic relationship with Zooxanthellae, just like other corals and so does Palythoa, and Protopalythoa. The later are more inclined to feed mechanically with larger foods verses the small polyp Zoanthus that feed through chemical absorption. These Sea Mats typically settle in shallow waters and receive a high amount of sunlight and UV radiation, most have a propensity for incredible coloration. We all have, or at least know, a lucky friend who has brought a piece of brown Acropora and had it turn blue in a few months. Polyps, in my experience, have acted much the same way, this being the main reason I look closely before discounting any brown polyps at the local fish store. In high nutrient conditions and poor lighting, the polyps can turn color very quickly to adapt  to their environment. One of my rules of thumb in studying a potential Zoanthus specimen for acquisition is to look for faint contrast zones, even if they appear to be a similar color. Most of the polyps encountered in nature have contrasting disc components, that is the mouth and the disc may contrast one another, or perhaps the tentacles. If you look closely at a specimen whose color has been muted from the absence of light, you still have a shot at identifying the contrast zones. The more zones you can count, the more color regions there are that have the potential to become definable under the proper lighting.

My most impressive Zoanthus has seven color zones, and when I purchased the colony the contrast regions were clear (from close observation). However, the polyp appeared to have a dull orange oral disk and with green tentacles.  

If you look closely, you can see that the light green mouth is surrounded by a zone of high contrast that looks to be a deep purple. The first ring on the oral disk is light orange, which almost appears to graduate to a darker orange. The disk’s final ring is in purple, repeating the contrast zone around the mouth. The tentacles begin in a light, muted green- the same color as the mouth, and finish in an incredible iridescent green. Such a display of color I find truly amazing. I found this colony locally for $25 dollars. It had about 20 polyps, but not near the impressive display that it has evolved to in my system. In about a year, I have traded no less than 5 fragmented plugs of this color morph for many more brilliant colors to expand my collection. You can see more than 25 color morphs that I have collected on my web site, under “Captive Propagated Species” in the “Coral Farm” section.

Sometimes, it is just as enjoyable finding a few polyps accidentally (that have come in as hitchhikers on another piece of coral picked up through mail order or from a local fish store) as it is coloring up a specimen. Zoanthus often come in this way because of the encroaching nature of colonies. The L.F.S usually does not separate them and grow them out they mostly sell the specimen as it came in. One of my greatest finds was on a piece of “Wood Sponge” or Placospongia. I actually saw a few polyps on the underside when I was purchasing the specimen, but they were closed and I had no idea what to expect.

Variety

Variety amongst the Zoanthus, in particular, has never ceased to amaze me. In the years that I have been collecting and propagating Zoos, I’m sure I have seen more than 100 color variations. Early on, most of my stock consisted of simple two-color polyps. Since then, I have narrowed down my brood stock to variations of four or more contrasting colors. There are exceptions, of course, to my interest. I am always on the watch for the “solid color” Zoanthus, or one that poses patterns or striations on the oral disk, and lastly just rare colors. Here are a few of my favorites that I have acquired over the years.

Aquascaping / Opportunities

Aquascaping a reef system presents many challenges to both the novice and advanced hobbyist. Some aspects, such as rock structure, are mechanical in nature, and can be solved though patience and  the use of zip ties.  Others can be a bit more daunting. Aesthetics- for example, specifically balancing color and texture, can seem impossible at times. I have always strived to keep a bit of everything in my display systems, and even with the most diverse collection, one can find oneself with a display leaning towards specific shades and tones. Most of my systems had been predominantly SPS, with some various LPS and exotic leathers. For the most part, my stony corals were either  Blue, Pink, Yellow, Purple, or Green. Green and Blue seemed abundant, and colors like Yellow had been limited to mostly Porites and Sarcophyton. I had a bit or difficulty pulling the eye away from such a dominant focal point, partly because the yellow color was scarce, and secondly, the Porities were large colonies compared to the other SPS. Nothing enhanced the display more than my dive into Zoanthus. With such a wide variety of color, I was able to balance out the look and feel of the tanks

Aggression

Zoanthus and Palythoa both contain very toxic chemicals,  that are dangerous to both reef inhabitants and humans. The most well known is Palytoxin, which has been documented as one of the most poisonous marine toxins known (Mereish et al, 1991). Palytoxin can affect the heart, muscles, and nerves leaving its victim in paralysis, and possibly death. Because of the toxin, you should never handle Zoanthus or Palythoa with open wounds, nor should you touch your mouth or eyes after handling the species. (Editors’ note: We recommend the use of disposable latex gloves)  When propagating either of the species, it is critical to remember that the slightest rub of an itchy eye, or even a small cut from a hang nail, might be enough to land you in the hospital. In the aquarium, some rapid growing Zoanthus colonies can be aggressive to stony and soft corals, but in general, they are very peaceful, and you can slow the growth rate by the controlling the overall nutrient load of your tank.

Growth Rates

In my years of observation of Zoanthus, I have seen some grow at tremendous rates while others were lucky to add on a few polyps per year. With the same size stock and oral disc you would assume they could have come from relatively similar conditions, and should respond in nearly the same manner. With Zoanthus, this could not be further from the truth, in my experience. Many of the color morphs looked identical but grew at totally different rates under the same conditions.

One example is a pink color morph specimen that is by far the most aggressive and rapidly-growing one I have worked with to date. I have witnessed the colony quickly surround a Blue Acropora abrolhensis and slowly kill off the tissue and begin encrusting on its base.

The second most aggressive morph that I keep is what I call “Actinic Yellow” . You can see in the photo that they are growing right along side of a piece of Heliopora. If you familiar with the coral, it’s a quick growing mass that can cover most everything in the aquarium. The Zoanthus polyps however, kept the colony of Heliopora’s growth in check along the side where the two meet. When the mouths would close at various times, you could actually see a series of half circles in the Heliopora that almost appear to be worn down from the polyps.

Feeding

Over the years, I have certainly experimented with a variety of foods. With pipettes and turkey basters, I would gently shoot a small cloud of over the colonies. While some tentacles would appear to grasp the food particles and wind inward toward the mouth, it was never perfectly clear whether is  was a reaction to the stream, or an actual feeding response. In the case of the large- polyped Palythoa and Protopalythoa, feeding is much more obvious.  

Soft shrimp pellets, for example, are taken readily, and you can see the tentacles grasping the food bits and closing in around the mouth and oral disk in just a few minutes. Upon completion of my dedicated system, I plan to study the direct feeding and growth rates of Palythoa, comparing two identical colonies- one being fed directly, and one not. Until  now , I have witnessed slow to moderate growth at best, in comparison to other polyps. Zoanthus, on the other hand, will flourish  and reproduce quickly with some intervention. While I’m yet to find if direct feeding can make an impact on some of the color morphs I have more trouble growing, I can say with confidence that keeping the nutrient load high in the aquarium expedites reproduction. From my observations in the case of most polpys, heavy feeding of fish seems to create a more conducive environment than any attempt at direct attempts thus far.