Growing reef corals is an endeavor for which there are many wonderful paths to success. Last month I proffered so-called "recipes" for feeding reef invertebrates, yet I am sure that there is no single "best" recipe overall for success with keeping aquarium denizens… only good ingredients. Its rather like bread making: given to ponder, you might be amazed to think of the many different varieties of bread in diverse cultures around the world, yet there is the common thread of a few simple ingredients to most all of them. I reckon that some aquarists with stressful jobs consider their relaxing aquarium nearly the staff of life too that bread is in our modern day! At any rate, whatever enjoyment it is that you derive from keeping corals, I intend to help you insure it.
To be successful as a reef aquarist, the literal growth of one's charges is an inevitable and pleasant dilemma. Life in stasis (without growth or decline) for coral is unlikely if possible at all to achieve if you doing your job properly. Moreover, it should be a great thrill for the aquatic gardener to bare witness to the fruit of his or her labor as corals prosper. Inherent with the prosperity of growing corals are new challenges for meeting the increasing demands of providing sustenance and the very escalation of interspecific aggression with cnidarians in the narrowing confines of the aquarium. We need to plan for success when keeping corals and other reef invertebrates. Before we can discuss how to manage growth, however, we must first discover how to achieve it.
The basic ingredients for growing reef corals successfully are: appropriate light, food, and water flow. Please remember, though, that all three ingredients depend on good water quality and competent husbandry to make a successful recipe. Indeed, good aquarium maintenance is the yeast that leavens our bread if we are to continue with our food analogy for realizing success with reef keeping.
1) The Delivery and Care of Reef Light and Hardware
Of the three main ingredients, lighting is the most commonly addressed parameter in reef keeping. In popular literature, it shadows the importance of proper food and water flow to the extent that some aquarists seem to focus only on this parameter to any significant extent. But again, success with aquarium corals is dependant on all ingredients addressed in concert.
It would be fair to say that most popular corals recommended to the average coral gardener are photosynthetic and depend on proper illumination for the bulk of their sustenance. Symbiotic species (with zooxanthellae) are generally easier for most aquarists to care for in contrast to the aposymbiotic filter feeders. Most symbiotic corals derive more than half of their nutrition from the products of photosynthesis and the translocation of carbon. In suit, lighting hardware is one of the most important decisions you will have to make in an effort to grow reef invertebrates successfully. Choosing the right lamps first depends upon making a list of targeted species for the display. Identified corals can then be evaluated to make a proper choice of lighting equipment to serve them. Otherwise, you will be limited to selecting your future livestock around a hardware choice. Buying lights before making the guest list of corals is really counterintuitive.
Once you have determined if you have a low, medium, or high light needs and then have selected appropriate hardware, good aquarium husbandry must support the effective delivery of light… every day! Please consider that regardless of how well suited your lamps may be above the water, all is for naught if the penetration of light is persistently compromised by poor water clarity (yellowing agents, turbidity, etc) or if the lenses and lamps are routinely coated with dust and salt creep. The best and brightest lamps in the world are merely a vehicle for funding the college tuition of your local electric supplier's children if you do not consistently export discolorants from the water and wipe the lighting hardware clean twice monthly or better. Good protein skimming, proper use of chemical filtration (small doses of media changed frequently), regular partial water changes ("Dilution is the solution to pollution.") and ozone are all helpful for maintaining optimal water clarity.
Another consideration is that the shock of a sudden increase in light from a tardy address of water clarity can be stressful and ultimately fatal to some corals. It is an underrated cause of "bleaching" (the expulsion of pigmenting symbiotic algae) and duress in many captive corals. You can imagine that it wouldn't take much to cause such an event; consider the hectic schedule that one has in the weeks before, during and after a holiday. In concert with some neglectful oversights with the rotation of carbon or tardy care of the protein skimmer, it is possible for a spell of 3 or more weeks to go by with little or no significant export of discolorants from the water. After this expended period of time and the escalating "yellowing" of aged water, a large water change and exchange of fresh filter media may send system invertebrates into light shock with suddenly improved water clarity!
There are, in fact, many considerations for the optimal illumination of corals. The details and nuances of this dynamic were covered in the September 02 issue of Today's Fishkeeper for suggested reading. There you will find a simple summary of lighting limits and recommendations to help you easily navigate through the blizzard of marketing that abound on this topic ("Lighting Reef Invertebrates").
2) Feeding corals… Not a Matter of "If", but "What and How Often"
In last months issue, Oct 02 TF, I detailed various elements of coral nutrition and recommendations for which corals need to be fed what foods. In continuation, I should like to proffer here basic advice on the proper application of foods for good coral health. Let there be no doubt that most coral need to be fed weekly if not daily. Nearly autotrophic corals are still not fully self-sufficient in symbiosis with zooxanthellae and, if unfed, they will starve to death in time… it just takes longer. Inadequate nutrition is often the reason for so-called mysterious deaths in corals after many "successful" months in captivity.
Good habits with food handling and preparation are critical to deliver useful sustenance to your growing corals. Most are not too inconvenient with due consideration. It is an ironic reality in the everyday that aquarists far and wide succeed in understanding and acquiring nutritionally appropriate foods for their invertebrates yet fail to deliver them successfully. Two of the biggest obstacles in reef husbandry with coral foods are perishability and prey size.
On the topic of food perishability, give similar consideration to your fish food as you would to items fit for human consumption. The most basic rule is freshness. The nutritive quality of all foodstuffs degrade in time with critical vitamins waning first and fast. Few if any foods keep well much past six months of age under the best circumstances. Ideally, buy prepared foods in portions that can easily be used in 2-4 months. Frozen foods and opened packages of dry food should be discarded after 6 months. This aspect of good aquarium husbandry is easily obeyed. However, proper storage of aquarium foods is another matter altogether! Dry foods should be stored in a cool, dry place in tightly sealed containers. They must although be protected from extremes of temperature and humidity. Unfortunately, many food containers are not so well designed that support from a zip-lock plastic bag would not make a great difference. It is inevitable to want to keep food containers nearby to the aquarium but few places close by are suitable. Light from the aquarium, if not indirect room and window light, quickly degrades the quality for foods stored in clear or translucent packaging. Atop the hood or light canopy is a dreadful place to keep a tin of coral or fish food.
Furthermore, the fluctuating temperatures near the top of the aquarium from day/night cycles of the lamps will also shorten the shelf life of foodstuffs tremendously. This reality is compounded by the humidity surrounding the aquarium which can quickly lead to spoilage of freeze-dried, flake and pelleted fare that you might not recognize for some time unless you snack on krill and fish meal with your captives! An even worse place for food storage is underneath the aquarium in an enclosed cabinet where the humidity can build high enough that moss and orchids sprout spontaneously. The best place for dry aquarium foods is simply in the refrigerator in a tightly sealed container. When this is not convenient, keep only small portions at room temperatures that can be used within weeks. Frozen foods should be stored with like consideration in tightly sealed packages (zip-lock bags are fine) and used within just a couple months. Any money saved on buying foods in bulk that must be stored for extended periods of time is lost on the degradation of food quality in time and the subsequent compromise to your animal's health. A disregard of good food handling is very ironic with corals in reef systems, which are some of the most expensive aquarium displays in the hobby; its like feeding the lowest grade kibble to a pedigreed dog.
Prey size is certainly the most underestimated aspect of coral feeding and one of the most neglected dimensions of reef aquarium husbandry at large. Corals that feed organismally (particles) often have a very strict range of acceptable prey size that can very down to the species level. Two Dendrophylliids, the yellow scroll coral (Turbinaria reniformis or T. mesenterina) and the common cup coral (T. peltata) are a prime example of drastically different feeding strategies between like species in the same genus. Both can occur in cup or scrolling morphologies and share grossly similar traits. Yet, T. peltata has enormous polyps and depends heavily on organismal feeding while the "yellow" related species feed very little if at all organismally (it is not uncommon for aquarists to observe that they rarely put their tiny polyps out). It is tantamount to research a coral's likely needs for husbandry before purchasing it.
In most cases, form clearly follows function and consideration of a coral's polyp shape and size will indicate suitable sized prey. Large fleshy polyps like we see on cup corals (Turbinaria peltata) and Elegant corals (Catalaphyllia elegans) are better suited to capture and digest large zooplankton and even minced chunks of meat of marine origin. On the contrary, the tiny polyps of some leather corals like many Lobophytum species are clearly unable to "grab" chunks of food from the water column. Also, take to heart that tiny polyped octocorals usually do not seem to respond to the sensation of large food particles nearby in the drift or upon contact (target feeding). Their relative indifference to organismal feeding is a clear indication that they derive their nutrition largely by other means (predominantly from photosynthesis and feeding by absorption). If you have any wonder if the food that you are feeding your coral is appropriate… simply observe to see that prey is being stung and digested. In some cases, excrement from the coral is an unmistakable dark, stranded expulsion (as with hearty feeding Fungiids) and proof positive that feeding was successful.
Beyond dry and frozen foods, liquid suspensions are offered in the market to aquarists too oft ill prepared to use them. With the recent popularity of bottled phytoplankton products brings the reminder of how the educated consumer if the best aquarist for our industry. When mentoring aquarists, I often refer to the "inappropriate and heavy" feeding of bottled coral food supplements with specific reference to phytoplankton substitutes. Some bottled phytoplankton products are very useful indeed but they are commonly misapplied and some may be lacking in instructions for proper application altogether. I have not personally conducted the studies on phytoplankton and bottled substitutes, but I have been enlightened by the reports of those that have. Notably, Dr. Rob Toonen has described that even the best bottled phytoplankton is effective in a very narrow range of application (whatever "best" is varies by species or nutritional composition for your individual purpose). The limitations of bottled food supplements have to do largely with "clotting" or coagulating of the matter as it ages, rendering the prey/product size too large for many of the fine polyped feeders. * Some recommendations for using liquid food/phytoplankton products: - They should ideally should be packaged, transported, sold and kept refrigerated throughout the entire chain of custody for the longest shelf life. Phytoplankton is especially sensitive to deviations and storage at room temperature. Spoilage can occur within days.
- Like most foods, the shelf life of bottled supplements is arguably 6 months at best after which time the efficacy degrades dramatically (particle size increases significantly). Such products are used best in 2-4 months. - With every application, the liquid food sample should be whisked in an electric blender to reduce particle size... hand shaken samples are largely ineffective. Mechanical whisking is critical for bottled phytoplankton in particular.
It is on this last point that most aquarists fail from lack of information. Most aquarists know not or will not commit to this tedious application and erroneously feed more of the suspension hoping for the best. In this manner, bottled supplements unfairly earn their reputation as "pollution in a bottle". Some defenders of the "no-blending" school of thought assert that the undigested or oversized particles still degrade into useful dissolved organics for corals to feed upon by absorption. I'll be the first to say that I am not qualified or interested to test that theory. But by the same line of logic, does that mean that small bits of dissolved cheeseburger also have some potential use? What of rotting algae… is that helpful just the same? I don't even want to form an opinion on such matters. If we are talking about offering a suspension of particles to an animal that feeds organismally (by whole prey/particles), then I would rather not make or hear excuses about the possible ancillary benefits of dissolved matter. The overwhelming practical and anecdotal evidence on this matter also reminds us that the abuse of liquid coral foods serves largely to fuel nuisance algae growths at any rate.
The best solution for aquarists in need of feeding fine zoo- or phytoplankton but unable or unwilling to whisk prepared liquid substitutes is to employ an upstream fishless refugium. Vessels with course media and regular feeding can generate larger zooplankton like amphipods and mysids. Sugar-fine sand or muddy substrates will encourage copepods while surge-pounded seagrasses can proffer epiphytic material and possibly phytoplankton. Dedicated aquarists and researchers might set up food culturing stations instead for rotifers or unicellular algae and drip feed their corals for optimal feeding.
There are indeed many options for feeding your corals but always take heed of particle size and prey suitability. The ultimate irony about the above mentioned misapplication of bottled foods is that many of the targeted animals are unlikely to even eat phytoplankton. The fact of the matter is that most of us have corals that decidedly favor meaty fare (zooplankton). So unless you have a herd of gorgonians or a gaggle of Nephtheids, I would resist dispensing bottled phytoplankton in my tank like it was fertilizer. 3) Water Flow… how much is enough?
On this last point (ingredient for success), I wish to offer you some simple guidelines on water flow as a foundation for a future installment, having covered feeding and lighting in specific address recently. Still… the summary for the successful provision of water flow to corals is really a very simple matter. In fact, water movement is perhaps the least controversial topic in reef aquarium science.
It is very difficult to have too much water flow in most reef aquaria, but it is possible to dispense inadequate flow improperly as to seem excessive. Most coral require strong random turbulent or surge motion. For these corals, a laminar or linear flow (one directional as we have from the spout of a power head) can be quite dangerous and literally denude flesh from a coral ill adapted to bathe in such a direct path. The exceptions to this rule are quite conspicuous as with the sea fans and gorgonians. Fan-like corals are morphologically adapted to live and feed in the brisk path of a laminar flow and have grown into a flat plane to exploit such water movement. For most other corals, however, it is safe and necessary to change and deflect the path of water variably.
The best application of water flow for most reef displays (traditional mixed garden reefs) is a simple random turbulent pattern with full time pumps or outlets (from a sump driven manifold) pointed directly in opposition to each other. Thus, a dynamic and random pattern of water flow is created throughout the tank by the convergence of these energies. Surging water flow is arguably better for many corals but not so much that it warrants the complicated and unsightly employment of overhead dump or surge devices. The interruption of water flow by wave timers and wave makers is equally unnecessary and categorically less useful than the proper full time employment of the harnessed pumps. Rest assured that the simple creation of random turbulent flow from converging powerheads, for example, will give you the most bang for your buck!