What Happened to all the Soft Corals?

Photo courtesy of Robie Sayan.

The first reef aquarium I ever encountered was quite a sight to behold. It was filled with a variety of colorful soft corals, the polyps and branches swaying to the rhythmic pulse of the currents. This aquarium caught my attention because it was so fluid; I was entranced. It was this tank that convinced me to set up a reef aquarium. Tanks featuring soft corals were all too common around that time. In fact, rarely did I see an Acropora or any other small polyped stony corals for sale at the local fish store. I remember that these types of stony corals were still considered very challenging and best left to knowledgeable reefkeepers with the best resources and husbandry skills.

My how things have changed! Significant improvements in reef aquarium technology and a better understanding of the needs of stony corals have allowed us to progress to a time where Acropora and other stony corals can not only survive, but also thrive. These significant strides in the hobby have led to mass propagation of these corals, allowing fragments to be shared with other reefkeepers. Today, tanks dominated by small-mouthed stony corals are everywhere one looks. Brilliant colors and shapes certainly make these tanks a sight to behold. But along the way, I've noticed a general decline in the number of aquaria dedicated to the corals that paved the way for the current state of our hobby. Rarely do I see a tank dedicated to soft corals anymore, and I feel that this is somewhat of a shame. The variety and beauty found among the Octocorallia are quite considerable, yet contemporary aquarists rarely incorporate many of these corals in a reef aquarium. This article is for those who still take the time and resources to appreciate these corals, and to also encourage others to perhaps dedicate an aquarium for them.

Why Keep Soft Corals?

Based on the husbandry skills needed to keep this group, soft corals have a lot going for them. With the exception of the non-photosynthetic species, many of the commonly available soft corals are more forgiving and easier to care for than smaller polyped stony corals. These include the Leather Corals (Alcyonidae), False Leathers (Paralcyonidae), Zoanthus spp., Rhodactis spp., Ricordea spp., and Discosoma spp. They will thrive under a variety of available fluorescent lighting fixtures, and tolerate lower flow rates than seen in typical small polyped stony coral aquariums. A total turnover of approximately ten times the total tank volume is more than adequate. Calcium demand is also much lower in a softie tank. One can avoid the need for a calcium reactor, as kalkwasser or a simple two-part additive solution will suffice. As a result of their more modest requirements, a reef aquarium dedicated to the "easier" varieties of soft corals is an ideal set up for a budding marine aquarist or someone that lacks the desire for a complicated display system.

Photo courtesy of Kris Duggan.

Soft corals also break up the monotony of the rigid stony corals. They offer movement and a different appearance. I remember while entertaining guests, how the first thing my company usually noticed in my previous tank was the large Colt coral swaying back and forth, or the carpet of green star polyps rustling in the current. Rarely would I ever hear a comment about the beautiful purple branchy Acropora colony growing nearby.

An interesting trait of some soft corals is that they are very toxic or distasteful to potential predators. Aquarists usually worry about the possible threats these chemicals pose to their stony coral colonies. However, it can be an asset in certain applications. Particularly noxious corals, such as Sarcophyton and Lobophytum spp., are usually unpalatable to many opportunistic corallivores, such as certain Angelfish and Butterflyfish. Both of these types of fish can wreak havoc on less toxic varieties of soft and stony corals, but one could create a wonderful reef display with these fish by choosing only toxic soft coral varieties. It should be noted that some corallivores, like the Teardrop Butterflyfish (Chaetodon unimaculatus) are unaffected by the majority of soft coral toxins. Furthermore, many Butterflyfish are obligate corallivores, which makes them poor candidates for captivity. On the other hand, some of the available species in these two families will readily adapt to food offered by the aquarist. However, their occasional nips on coral specimens can add up to a lot of damage in a confined reef aquarium. In such a scenario, the use of more toxic varieties of soft corals could allow for a pleasing display without much damage from tankmates' feeding habits. Clownfish will also adopt many soft corals as surrogate hosts when a suitable anemone isn't available. This offers a neophyte aquarist a clownfish host alternative to the more delicate anemone species.

Lately, there are signs of a renewed interest in soft corals. There is a great demand for colorful Ricordea, Corallimorphs, and Zoanthus spp. Hopefully, we'll see more soft coral dominant tanks in the future. They are an attractive alternative to the multitudes of small polyped stony coral dominant tanks.

A final word about soft corals: in this article I have categorized them into a broad group. It is important to note that individual species can have vastly different requirements to thrive. Please research the requirements and needs of the corals you wish to purchase, and any livestock, for that matter. Some notable softies to avoid are the Dendronephthya, Scleronephthya, and other aposymbiotic soft corals. Some heterotrophic softies are able to thrive in a reef aquarium, but are less forgiving than the softies mentioned in this article. For example, I have found that Gorgonians and Xenia are a little more demanding when it comes to light and current. Always decide first what you intend to keep and then design your aquarium accordingly.