Dendronephthya aquaculture beginnings
Dendronephthya aquaculture beginnings
Hello everyone!
I've been exploring conditions for growout of Dendronephthya frags. Specifically, I wanted to concentrate on how to clone and grow out Dendronephthya because Scleronephthya clearly requires different conditions for optimum culture (larger particles and clearly at least some and perhaps all zooplankton and lots of it). So, the optimum aquaculture conditions of Scleronephthya, Nephthyigorgia and related "larger polyped" NPS organisms should be a different thread. That is, this is a "small polyped" aquaculture thread for Dendronephthya.
The first thing I want to report is that Dendronephthya frag easily. It's important to select a branchlet of about 25 polyps with a good firm base. The base diameter is important because Dendronephthya will "autofrag" by collapsing strongly and autoamputating these branchlet clones. Branchlet cloning is one of their natural reproductive methods and it is helpful to take advantage of this. However, if you don't choose the base carefully, it will go on to autoamputate further. With practice, you'll learn how to choose the best branchlets.
Another question is when to frag. Since Dendronephthya will typically start autofragging as soon as they arrive in a new setting as a stress response, it's an interesting question as to whether such immediate branchlet amputation behavior is as good for the parent colony as it is for the survival of the clonal line. I think that it is; that is, I think fragging a Dendroenphthya on arrival is good for the parent colony. This is a matter of experience, and an opinion rather than any controlled studies. In my opinion, it is a good idea to begin fragging any Dendronephthya on arrival using proper branchlet selection. The worse it looks, the more it should be fragged.
Attachment is another issue where I think there is progress already. They attach readily to any smooth surface such an undefended PVC. They do not accept cyanoacrylate. I have had best success by using the PVC coral plugs that fit into egg crate. (By the way, they only fit into the white eggcrate, not the black). I use the small rubber bands to hold them onto the cup, place them in a quiet area, and they will attach within three days or so. I leave the rubber bands to dissolve in place.
Regarding orientation of clones, there is one scientific paper that noted much better survival of clone recruits on vertical rather than horizontal surfaces. Chuck Stottlemire has called this observation into doubt (pers. communication), suggesting that at proper flow orientation doesn't matter. However, I suspect it does matter. Something to look at over time. I prefer to grow out frags by hanging the eggcrate vertically, or placing it at a strong slant in the tank.
We need a simple, optimal system for growing out clones. I have started an experiment recently on an extremely simple system and I hope some others will follow along and try this yourself so we will have more than one site to collaborate on. The description of the system follows:
I am using a 55 gallon aquarium, no substrate, glass covers across all but one inch of the top and two flourescent strip lights (one four foot and one three foot bulb- it's what I had). Water movement is with a single Koralle prop pump (largest one) placed at one end. I used water from the main system, which already has NSW values for silicate, 10 ppm nitrate, and 2 ppm phosphate, pH 8.3. I left the strip lights on continuously. The next weekend I measured pH 8.4 consistent with photosynthesis, and a very light growth on the glass sides and in the water. I scrubbed the film off into the water column, and have continued to do so regularly. Since the nitrates did not fall over one week, I added a few drops of Kent's Iron (also has molybdenum) and, a few days later, a few drops of Florida MicroAlgae Grow (a general microalgae inorganic fertilizer) and mounted one Dendronephthya frag of 25 polyps which had previously attached in the main system. The frag is mounted on eggcrate with a PVC coral cup holder and a rubber band, and has a good base. I placed the rack at a slant close to the pump. (I have found that Dendronephthya particularly like the intake rather than the outflow of any pump, even a prop pump, as the flow pattern is very laminar in this area).
This propatation tank is fairly clear looking though the tank, but has easily noticeable green turbidity looking down the long end. In my experience, this visible green tinge on the long axis of a 4 foot tank is an adequate cell count for growing Dendronephthya, and an easy way to estimate food density.
There is no heater or any other device on this tank. I believe the glass cover for carbon retention, and the continuous but modest amount of light, are both helpful (higher amounts of light in the past lead to pH instability and aggressive growth/crash cycles of phytoplankton). I am happy with a pH of 8.4 indicating a tilt toward photosynthesis. Also, I suspect that the lack of substrate is necessary to maintain a continuous phytoplankton bloom under relatively low nutrient conditions; it's easy to get greenwater under higher nutrient conditions but this is typically a pest species such as a pelagic cyanobacteria that may grow aggressively and let off allelopathins. There is much to understand about why sand bed unskimmed systems have failed to keep Dendronephthya before- and why Tyree's system couldn't keep them- more on this later).
There is a slight slick on the surface which I intend to leave as a possible food source for the frags.
This clone seems to go through an inflation/deflation cycle about every hour or so, much more rapid than the larger specimens in the main tank. Polyp extension is excellent, and the attachment site appears to have thickened to me. In any event, it certainly has not regressed.
A few days ago, I was doing my daily polyp count when I noted a dark spot at the base of the closest polyp (which as a previously single polyp was itself projecting directly out from the base), suggestive of a new polyp formation. This is a process I have watched for hours, dozens of times, under various lenses and boom stereomicroscopy, so I am familiar with it. It can be difficult to tell whether it is a new polyp, or just a small one that wasn't previously expanded. However, I watched this spot come together over the last two days, using a hand lens. Tonight I got up to look again (I know, this is not normal human behavior) and noted the first appearance of the new polyp.
I believe this clone is adding polyps, signalling (if this bears out) that it is probably in positive caloric balance. If this success continues over the next few weeks, I will move more clones into the system.
Of course the long term stability of this simple system remains an open question. What nutrient fertilization regime allows optimum growth and prevention of pest algae species? Is the available pigment spectrum adequate for coloration, and if not, what are the physical parameters within which a gradient of pigments would be elaborated (i.e. is the depth of the tank important in generating a light gradient which causes a phytoplankton gradient on the glass walls of the tank?). Will zooplankton type feeding be needed for growth at some point, or will microaggregates and the populations on the surface slick be adequate? (If anything other than inorganic fertilizer needed to be added, it would really mean the simple growout system wouldn't be practical).
I hope some others of you will join me in setting up these experimental simple Dendronephthya aquaculture systems. You can do controlled trials in as little as ten gallons, using the smallest prop pumps. Multiple sites will be helpful in getting the Dendronephthya aquaculture effort going, and we can begin to exchange not only information but also frags. (The optimum way to ship frags is something we should explore- at least some species have some intertidal survivability, so they may be able to be shipped by the "dry method"- I haven't tried it yet).
I'd also like to make a prediction. Within three years, there will be an explosion of interest in these "orchids of the sea" and a new type of aquarist will begin keeping optimized Dendronephthya-only aquariums, exchanging exciting clone variants, and selecting clones for traits. This will grow directly out of what we do here on this site. All of you participating in the NPS forum should look forward to the day when your efforts pay off like this. Come on, get out your old used tanks, and start an experimental Dendronephthya aquaculture site!
:rollface:
