Propagating Stony Corals

Introduction

With increases in the number of reef aquarium hobbyists over the past decade, there has come increased pressure on the natural reef systems of the world. The large demand for stony corals by reef aquarium owners have led to the partial destruction of some reefs as suppliers attempt to make these corals available for sale. In addition, many of these corals will die in transport and some of the remaining will die during acclimation to our aquariums. Many are surprised to learn that up to 80% of the corals harvested will die during collection, storage, on route, or acclimating in our tanks.
While the natural reefs are a renewable resource, it appears they may not be able to keep up with demand by hobbyist at a time when increased pressure from other sources (such as nutrient import) are also causing great damage. In the near future this may indeed lead to regulation and even moratoriums on coral imports. This of course would be a major blow to reef aquarium enthusiasts as the price, and finally availability, of the corals we wish to keep goes beyond our reach.

Why Propagate?

The natural solution to this problem is for hobbyists, in large numbers, to propagate the corals they already have. If successful, we can increase our stock and diversity through sale and trade. In addition we can learn much about the needs and characteristics of the corals by propagating them. Also, as some have found, propagated corals end to acclimate easier and faster to our aquariums with fewer deaths.
So I feel it is a moral imperative as well as a pleasure to propagate the corals I own and with this article I hope to share some of my experiences and possibly encourage others in the hobby to propagate theirs. After having run a successful reef aquarium for several years, I decided I would try coral propagation. I already had a reef system full of thriving stony corals including many Small Polyp Scleractinia (SPS) types with most of these from the genus Acropora which I knew were being propagated by others. The question of course is HOW were they being propagated? What special tools or techniques were being used? I needed to do some studying before attempting this task.
I began my research into propagation by visiting the Geothermal Aquaculture Research Foundation (GARF) web site. Here I found a wealth of information on stony coral propagation based on research done by the GARF folks. I felt I could apply their recommendations to my corals and so began several trials. After success with these I began to propagate SPS corals in larger numbers and now I have also propagated several Large Polyp Scleractinia (LPS) corals including the Trumpet Coral (Caulastrea echinulata)and Frogspawn (Euphyllia divisa). The end result has been to generate more information by experience and to increase my stock of corals. In addition I have traded many coral frags and grow-outs with fellow hobbyist and sold some to a LFS which helps defray the cost of running the reef system. In any event, I have reduced the pressure on the natural reefs (albeit in a very small way) by making available a second source of corals - Aquacultured corals!

Terminology

There are a few terms that need definition before we can proceed. Some of these terms may be in dispute amongst knowledgeable hobbyists but will serve for this article.

• Host - This is the coral colony that a cutting or frag comes from. It is often first generation but may be of any generation.
• Cutting/Frag - This is a piece of a coral that has been separated from the host and usually contains a small fragment of skeleton and tissue.
• Plug - A cutting that has been attached to a rock or other base.
• First Generation - This refers to the line of secession for a frag or cutting. A first generation cutting comes from a coral colony that was taken from the natural reef.
• Second Generation - This refers to cuttings that are taken from a host that was grown from a cutting that came from a first generation coral. Additionally, third, fourth and subsequent generations all refer to corals grown from cuttings from the previous generation.
• Grow-Out - This refers to the process of growing a colony from a cutting or frag. This process can take some time and results in a non-first generation coral colony.
• Attached Cutting - This refers to a coral frag or cutting that has been attached to some kind of base like a piece of live rock.
• Encrustation - For the purposes of this article a distinction is made between tissue growth at the branches of a coral and at the base. The base tissue growth will be referred to as encrustation growth.

Preparations

Before we can begin propagating corals it is necessary to have a good foundation for coral growth. This means an establish reef tank with stable parameters and a history of successful, and preferably rapid, coral growth. It will not be possible to propagate stony corals if the hosts themselves can not grow well.
Most experienced hobbyist know the general requirements for a well run reef aquarium. There are two though that I feel I need to empathize for coral propagation. The first is lighting. I have found that the frags seem to need at least as much if not more light than the host to insure good recovery and early growth rates. The frags also do well with increased actinic blue lighting (light with a wavelength of around 430 nm). So it may be necessary to put the grow-out frags nearer the light source or even add additional actinic light for faster growth. This is particularly true of Acropora spp. which will need a great deal of light energy to rapidly encrust at the base. In short, I have never had a grow-out do poorly because of too much light!
The second requirement for stony coral growth is good water flow. I prefer a pulsed or wave action if possible and this can be done by use of a wavemaker or surge system. I have found that attached cuttings grow better with this type of water motion as it is more efficient at removing waste products and stimulating the important base encrustation process.

The Grow-Out Tank

Some advanced hobbyist are using grow-out tanks to provide a more controlled environment for their frags. These tanks provide the same high quality water parameters and low nutrient levels of their main tanks but do not contain any coral predators or irritants such as snails or algae's. The tank design allows the hobbyist to work with the coral grow-outs without having to reach around host colonies or find suitable locations for mounting. There is more flexibility as to lighting and water movement and greater ease for target feeding of the corals.
There are a lot of good reasons to set up a grow-out tank and the hobbyist who does will be rewarded for the effort with increased growth rates and reduce losses. The down side of course is that it will require some effort, time and money to put one together. If you plan on doing a lot of grow-outs I would definitely recommend a dedicated grow-out tank. If you plan to just make several cuttings or are just starting to experiment with propagation, I would recommend that you just put the grow-outs in your main tank. This in fact is what I have been doing with great success for almost a year (though I do have plans for a grow-out tank in the future). In other words there is no requirement for a grow-out tank to successfully propagate corals, but it does offer advantages.
There are basically two configurations for a grow-out tank. The first is the attached tank. This is a tank that is plumbed to the main system (usually through the sump) and so uses the same water as the display tank. The second is the detached grow-out tank and is a self-contained system. There are advantages and disadvantages to both systems.
The advantage to the attached system is that the grow-out tank will have a larger system-wide water volume with the same water parameters as the display tanks. The disadvantage is that any problem that shows up in the display tank system (from parasites to poor water quality) will be reflected in the grow-out tank. Also, because of the plumbing, it may be difficult to find an appropriate place for the attached tank.
The advantage of a detached grow-out tank is the flexibility in its location. It could be in a different building if need be! The big disadvantage is lack of system water volume with all the negatives that implies. Also, there is a greater start-up cost due to additional equipment (like protein skimmer).
Regardless of the configuration, the grow-out tank can be made of any reef safe material and does not have to be the traditional glass aquarium. There is no imperative to be able to see in from the front or sides so plastic, wood or concrete will serve.
It is best that the tank have a large surface area and does not need much depth. This is so more corals can be put in without running the risk of neighbors stinging each other. The tank can be outfitted with racks made of eggcrate to help segregate corals of different types and light needs. A grid can be made of nylon string to help monitor growth rates. In short the grow-out tank can be designed to meet your grow-out needs with out paying attention to appearances.
There is no need for any live rock or substrate if you have an attached tank (all biofiltering will be done by the display tank). The unattached tank may need more thought in this regard though. It is unclear how successful a 'sterile' grow-out tank would be. I would recommend some kind of biofilter and the facility to add carbon. Lighting would be of a type and magnitude for good coral growth. This would be similar to the display tank lighting. Water movement would be done through a surge or wavemaker device.

Asexual Propagation

Before going into man-made propagation techniques, I want to look at several techniques the corals themselves have for asexual propagation. There are five know ways for stony corals to asexually reproduce -

• Polyp Balls - The coral creates a 'bud' containing a tumor-like sac of tissue and a small fragment of skeleton. This develops over time and, due to its weight, will drop off and become an independent coral.
• Fragmentation - Branching corals like Acropora and Hydnophora spp. can have branches break off by any numberof causes. Corals with thick tissue (like Hydnophora spp.) can sometimes have the skeleton break with the tissue still attached. In time the tissue will degenerate and the fragment will let go from the host. The fallen fragment is not dead and will, in time, begin to encrust to the surfaces it is contacting, forming a new coral. Hobbyist take advantage of this form of asexual reproduction to propagate their corals.
• Fission - Some sorals (esp. mushroom corals from the family Fungiidae) are able to split into two or more colonies during the early stages of their development.
• Polyp Bail-Out - In certain situations (usually stress), some stony corals like S. hystrix and P. damicornis may release single polyps. These will drift to new locations where they settle and can form new colonies.
• Brooders - Asexually brooded planula larvae may be developed by a kind of budding.

SPS Coral Propagation

I have propagated several SPS type corals over the past year and have found the process to be both simple and rewarding. The tools required are nothing more than a pair of diagonal cutters, a tube of Super Glue Gel and some small pieces of live rock rubble.
I have sold and traded grow-outs from 8 different species. I have avoided taking cuttings from a first generation host and selling them directly. Though I know some do this, it seems risky in that the host usually is not given time to acclimate and start growing before the cuttings are taken. One also losses the sense of husbandry while watching the small attached frags become full coral colonies. In addition, there may be benefits to the grow-out coral when compared to the frags. It appears that the growing second (or more) generation coral adapts to the high DOC and NO3 levels in the system and may be better suited for trading or selling to a new reef aquarium. In general I have found that the longer the grow-out period, the greater success the coral will have when transported to another aquarium. So I would recommend that attached SPS coral frags be allowed to grow-out in the same aquarium (or an attached grow-out tank) as the host for 6-9 month before being traded or sold. At a minimum, the coral should have good encrusting growth (enough to cover the glue at the base) and at least a few branches started before sending to a new home.
As I commented before, it is very important to have a stable, mature, reef system before attempting to propagate corals. This is needed since coral fragments seem to be more sensitive to changing water conditions than the host. In addition, mature aquariums are more likely to have some amount of phytoplankton and other water born nutrients for the polyps to feed on. The best measure of tank readiness is continued healthy and fast growth of the host corals.

Summary of SPS Propagation

• The Ross Super Glue Gel worked out real well. In fact the whole process only took about 15 minutes to do.
• Make sure the host is healthy, acclimated and growing well before attempting to propagate.
• Think about putting together a grow-out tank if you plan on doing a lot of propagating.
• Use surgical gloves when handling the cuttings or host.
• Handle the frags with light pressure as not to damage the corallite walls.
• Take cuttings from lower branches since these generally receive less light due to shading of upper branches and, if left on the host, will most likely die in time anyway.
• I found that, for S. hystrix, the small single branch frags did poorly. All had tissue death from the base up in one week. Make cuttings with at least two branches.
• Use small pieces of live rock with a little coralline algae on them for best grow-out appearance.
• Put several frags of the same species on one rock to increase the grow-out colony density.
• For Acropora spp. with fast growing branches, attach the frag sideways or horizontally to the base or rock. This will increase the encrusting area and will allow a more natural look to the grow-out.
• For increased support, bore holes in the rock or base then glue the cuttings into the holes. This is particularly important for corals that do not have aggressive encrusting growth.
• Allow the super glue to set over night with the attached cutting located in a quite place in the sump.
• When putting the attached cutting into the tank, be sure to secure the live rock with epoxy putty for long term stability.

By John Rice