The Temperate Reef Tank - Part One
The non-tropical reef system has unique qualities and special requirements.
The reef aquarium craze that erupted years ago in the United States has developed into its own significant niche in the aquarium hobby. This development has provided a welcome relief from the standard bleached-coral, crowded-with-fish look, and has spawned tremendous advances in filtration and other aspects of aquarium systems. A well-maintained tropical reef aquarium is certainly a thing of beauty that awes even the most jaded viewers.
All is not well, however, in the world of the tropical reef aquarium. Corals and live rock, the backbone of these systems, are not renewable resources — at least not on the short-term basis of decades. This has led to concern that repeated collecting for the aquarium trade could have potentially harmful consequences for delicate tropical reef habitats. The hobbyist who wishes to establish a miniature tropical reef therefore faces escalating expenses and possible difficulty in obtaining specimens.
Few aquarists are aware that the Pacific coastal waters of the United States teem with an incredible variety of fascinating fishes, invertebrates and seaweeds (algae). Pacific coast kelp forests and intertidal zones are among the most productive habitats on earth. Beneath the towering spires of giant kelp in the plankton-rich water, colorful sea stars, sponges, tunicates, anemones, bryozoans and a host of other invertebrates and seaweeds paint rocky reefs with brilliant mosaic tapestries of life. Numerous types of fish also go about their business within this busy ecosystem.
Public aquariums have provided the sole opportunity for most people to witness this magical world. A major obstacle has been the lack of suitable refrigerated systems marketed for the hobbyist. Even those who possess such systems are faced with the daunting task of obtaining specimens, as few fish shops and wholesalers can provide them. With the exception of a few aquarists who collect their own specimens, hobbyists have largely been excluded from maintaining these animals.
This is beginning to change. The advent of relatively inexpensive cool water systems and the increase of professional collectors who can provide greater availability of certain kelp forest creatures should make it possible for more hobbyists to take on this new and exciting challenge.
Comparison Of Tropical And Temperate Reef Systems
If you find yourself developing "cold" feet over the prospect of maintaining a miniature temperate reef, remember that the basics of aquarium care that apply for tropical systems are equally valid for temperate aquariums. There are, however, notable differences that should be understood when making the transition. Pacific coast water is unpleasantly cold, a fact that becomes immediately obvious when plunging into the surf. Heating an aquarium is an easy, inexpensive prospect that even the neophyte aquarist can generally manage. Unfortunately, cooling an aquarium requires a far greater expense and a somewhat elaborate refrigeration system.
As noted above, temperate fishes and invertebrates are more difficult to obtain than their tropical counterparts. It is ironic that for most hobbyists, it is a far simpler task to acquire exotic fish from the Philippines than those residing only several miles away in a coastal kelp forest community. Several companies do offer temperate animals (primarily for educational and scientific use), but they are not linked to any great extent with the aquarium trade.
As a consequence of their rare appearance in the aquarium trade, temperate animals are largely unknown to most hobbyists. Whereas many aquarists can cite hundreds of different freshwater and marine tropical species, most would be hard pressed to come up with the names of more than a few temperate fish. Public aquariums are excellent sources for learning firsthand about temperate fauna.
Temperate animals are remarkably hardy and easy to keep, and will frequently tolerate lapses in water quality that might mean the demise of more delicate tropical species. This, of course, must not be an excuse for their neglect, and every effort should be made to provide a comfortable environment.
Within tropical coral reef habitats, corals (and more specifically the symbiotic algae residing within their tissues) require high-intensity sunlight. Temperate habitats lack invertebrates with such a strict requirement. With few exceptions, standard aquarium illumination is sufficient. For those aquariums with seaweeds, adequate lighting is a must, but is generally far less intense than that required for satisfying the needs of reef-building corals.
Lastly, for the most part, temperate fishes cannot compare with the bright, gaudy coloration of many tropical species. This in no way should diminish interest in them, because they possess their own beauty that transcends a lack of brilliant hues. Temperate invertebrates have taken far greater artistic license with their coloration, and exhibit a bewildering array of bold reds, yellows, blues and oranges. Within the aquarium, wildly diverse creatures add splashes of color that equal or even surpass anything their tropical cousins can display.
Requirements For A Temperate Aquarium
Whether you are keeping goldfish or corals, the basics of aquarium care rest on the same fundamental concept — maintenance of good water quality. Aquarists who have successfully kept other types of aquariums should be quite capable of switching to a cold water aquarium, as the methods of water quality control are identical. Perhaps the major adjustment is in dealing with numb hands after a session of inside glass cleaning!
Biological control of ammonia and other fish and invertebrate wastes is critical to success, and can be accomplished with standard equipment, such as an undergravel filter. More advanced hobbyists may wish to dabble with the trickle filters and protein skimmers popular in tropical reef systems.
Regardless of the hardware chosen, all that is required is a method to control wastes. In fact, simple systems can provide marvelous results. Maintenance of nitrate levels below 10 parts per million (ppm) for tanks containing invertebrates — somewhat higher levels are acceptable for fish-only tanks — and redox above 300 millivolts indicate success in this endeavor.
Accessories to the biological filter can only help to improve your chances of success. Two of the most helpful are carbon filtration and a foam fractionator (protein skimmer), which do an excellent job in reducing the load of harmful organic compounds. Mechanical filters, such as outside canisters or power filters, help to reduce the load of organic particles that would otherwise be mineralized to ammonia.
Mention coldwater tanks and most people are intimidated by the prospect of setting up and using a cooling system. In the past, there probably was some merit to this fear, as units were bulky and inconvenient. Newer models are no more difficult to use than a canister filter. Cost is still a consideration, however, as refrigerated systems are by no means inexpensive. On the other hand, the popularity of tropical reef systems attests to the willingness of many hobbyists to overlook cost when a stunning aquarium display is the result. In fact, some reef enthusiasts employ chiller units to cool their aquariums during hot spells.
Pacific coast fishes and invertebrates are accustomed to a temperature range from 50 to 70 degrees Fahrenheit, depending on the location. Most can function quite well from 60 to 65 degrees, which is a good range to shoot for in the aquarium. Hobbyists residing in cool coastal areas may be able to accomplish this without refrigeration, particularly in the winter.
Many temperate animals can tolerate temperatures up to 72 degrees Fahrenheit even when they normally reside in water temperatures of 50 to 60 degrees, provided the transition is gradual. In the long run, however, the ideal solution for temperature control is a refrigerated system.
The heart of any chilled system is the heat exchanger. In this system, heat from the aquarium water is transferred to the refrigerant gas within the coils of the exchanger. The exchanger is frequently housed in a canister external to the aquarium (usually in a package containing the compressor and other components of the unit), but may also be custom built within the tank.
Rather than using potentially corrosive copper coils, the best units for marine aquariums incorporate non-corrosive titanium exchangers. Resin- and plastic-coated copper coils are a second-best alternative, but suffer from reduced exchange efficiency and a chance of cracks in the coating that will expose aquarium water to the copper tubing. Larger aquariums require correspondingly more powerful chiller/compressors.
The difference between room temperature and the desired aquarium temperature also plays a part. For a typical temperature differential of 10 to 20 degrees Fahrenheit (i.e., water temperature 60 to 65 degrees, room temperature 70 to 80 degrees), a 1/6th-horsepower compressor should suffice for up to about 100 gallons. Charts are available for determining the compressor size for other situations.
Every effort should be made to increase the efficiency of a chilled system. Areas within the system exposed to room air are sites for heat to enter, thus increasing the load on the chiller. Foam-filled fiberglass aquariums are ideal for insulating against heat gain, but most hobbyists have glass or acrylic tanks. Styrofoam can be attached to the outside walls of the tank, as well as the trickle filter reservoir if there is one. A fan must be installed in the cabinet that houses the compressor in order to reduce heat build-up. Foam insulation for tubing should surround all exposed water lines from the chiller to the aquarium.
There is one other consideration you should take note of. As you are well aware, if you take a glass of water from a refrigerator into a warm room, water droplets soon condense on the outside of the glass. This can also occur with a chilled aquarium, particularly in a hot, humid room. One solution to this annoying problem is to use an aquarium constructed with a half-inch-thick acrylic viewing window. Acrylic acts as an insulator so that the outer surface remains near room temperature.
With a glass aquarium, the best method is a double-paned viewing window with an insulating air space. Obviously, the standard all-glass aquariums available in stores will not contain this type of glass. Unless you don't mind continuously wiping water droplets from the front glass, acrylic is the easiest and probably most sensible way to counter condensation.
A cheaper alternative to a chiller unit is to adapt a small refrigerator for this purpose. While not as efficient or elegant as a commercial chilling unit, with some ingenuity it is certainly possible to construct a functional system. Typically, a hole is drilled through both sides of the refrigerator, a coil of tubing (not copper) is placed inside, the inlet and outlet tubing is sealed in place with silicon cement, and a pump or filter is used to circulate water from the aquarium, through the tubing and back to the tank. The combination of the temperature setting in the refrigerator, the amount of tubing in the coil (approximately 100 feet) and the flow rate of the water is used to regulate the temperature of the water.
Obtaining Temperate Animals
The difficulties many aquarists experience in obtaining temperate fishes and invertebrates is probably the greatest obstacle in setting up a temperate reef aquarium. With increased interest and demand, temperate fauna should become more readily available as regulated professional collectors establish links with fish wholesalers and retail shops. Of course, I do not wish to advocate ecological harm as a consequence of unscrupulous collecting methods. Only those species that occur in sufficient abundance to be negligibly impacted by collecting should ever be harvested.
It is beyond the scope of this article to examine methods for collecting your own animals. First and foremost, you must have a thorough understanding of fish and game laws for the area in which you wish to collect. Self-collecting can be fun and adds a new dimension to the hobby when you can provide the animals for your own aquarium. Unlike many tropical tanks with animals originating from widely separated areas, a local habitat aquarium is endowed with a special ecological unity. You also have more control over the entire operation, from collection to placement in the aquarium, resulting in less stress to the animals.
Drop in on any kelp forest and you will be immediately impressed by the constant surge, enough to cause sea sickness in some people. Sessile (sedentary) invertebrates and seaweeds are entirely dependent on this water motion to bring in food and nutrients and carry away wastes. Without the life-giving flow, most would quickly decline and become blanketed by fouling algae and other organisms. In addition to the health benefits, water motion within a home reef system also creates a more natural and pleasing aesthetic effect.
Within the aquarium, a back-and-forth surge that mimics nature is actually a relatively difficult undertaking. It is easy enough to establish a uni-directional current using a powerhead, but this provides flow and turbulence within only a small volume of the tank. Most seaweeds and certain sessile invertebrates, such as anemones, will benefit when placed in front of such a flow. However, two powerheads connected to a timed controller that alternates the two creates a more natural effect.
The best results are obtained when the bulk of the aquarium water is moving at any given time. Systems that employ paddles or pistons in chambers outside the aquarium can approximate this effect. They provide a more uniform, natural back-and-forth movement of water and reduce the chances of dead spots behind the rocks. Dump tanks that tip over or start a siphon when filled on a cyclic basis are another effective means for stirring the water, but in a manner more akin to waves breaking in the intertidal zones.
Adequate lighting is a constant source of concern for tropical reef aquarists, and numerous lighting systems have evolved to satisfy their needs. Aquarists wishing to house only temperate fish and invertebrates can dispense with this concern and utilize lighting solely as a means for illuminating the display. Seaweed enthusiasts will require somewhat more attention to lighting, but not nearly as much as that needed for corals and other light-loving tropical species.
Temperate seaweeds that do well in the aquarium are generally subtidal species adapted to relatively low light levels. Most of these belong to the red algae group and make very attractive display additions. Within the kelp forest, light levels below 30 feet are usually much less than corresponding depths in coral reefs.
A pleasantly simple system consisting of two 40-watt fluorescent tubes (one actinic blue and one cool white are a good combination) on a 12-hour cycle should be adequate for a 50-gallon tank — three tubes should be fine for 100 gallons. Low light levels have the additional bonus of reducing the growth of tenacious fouling algae. Metal halide lamps are unnecessary, and can, in fact, harm seaweeds accustomed to low illumination.
Establishing A Temperate Reef Aquarium
A key to success with a temperate aquarium is to proceed with patience and care. Establishing a piece of the rocky reef should be a methodical progression that is enjoyable to watch as it evolves and develops.
The backbone of the temperate reef is the underlying rock, usually granite, shale or sandstone. Temperate rocks are denser and less porous than the calcareous live rock of coral reefs. Only softer forms, such as shale and sandstone, have anything approaching the labyrinth of holes permeating tropical live rock. Whereas live rock is an important biological component within tropical reef aquarium systems, the role of invertebrate-encrusted rock is reduced in the temperate system. The primary function is to enhance the display and serve as a site to attach invertebrates, and secondarily to provide beneficial nitrifying bacteria during the breaking-in period.
There is no hard and fast rule on the proper amount of rock to start with. The base of the framework should consist of bare rock (beach granite is good). Subtidal or intertidal rocks with a light coating of invertebrates and encrusting coralline algae can be placed on top of the base rocks. Avoid rock with large sponges, tunicates or other sensitive invertebrates that could foul a virgin system.
The best procedure for handling any rock with living material is to house it in a separate holding system for several weeks to ensure that growths destined to perish do so outside of the main aquarium. The substrate can be anything you would use for a tropical tank. In some localities, calcareous shell beach cobble can be found and cleaned for a very attractive bottom cover.
Test the water for ammonia a day or two following the addition of rock with attached animals. If ammonia levels are low, you may begin the slow process of constructing your temperate reef. Invertebrates, such as anemones, sea stars, snails and crabs, are good additions for the six- to eight-week nitrifying bacteria establishment phase. Hardy fish, such as rockfish and sculpins, are also excellent for this purpose. Illumination may be kept to a minimum during this period as an aid in reducing fouling algae growth. In the event that unsightly filamentous forms do begin to proliferate, grazing snails and urchins can be introduced as control agents.
As a result of the colder temperatures of the temperate system, complete maturation of the biological filter may seem to proceed at an agonizingly slow pace. It will certainly occur with patience and the avoidance of system overloads. When the system has matured, you can complete the reef with steady additions of quarantined fishes and invertebrates. Rocks with denser assemblages of life may also be added after a suitable isolation period. Seaweeds are best attempted at this point, and the lighting should then be boosted to the appropriate level.
Quarantine For New Arrivals
Isolation of fish and invertebrates prior to their addition to the display is certainly a prudent endeavor for any type of aquarium. This enables you to determine whether all specimens are fit for the main display and also acclimates them to aquarium conditions (particularly if recently collected).
Parasite control is most readily accomplished at this stage. A chilled quarantine system is ideal, but must be completely isolated from the main tank. In lieu of this, keep the tank in the coolest location of the house. You may also be able to rig up a system in which the line from the chiller is routed through the quarantine tank (to act as a cooling coil) prior to entering the main tank.
Invertebrates may be confined for a week or two before placement in the main tank. This increases the likelihood that only viable specimens enter the display. Fish should be isolated and treated to ensure against the potential introduction of parasites. Temperate fishes are remarkably free of the disease and parasite problems that plague tropical species. External parasitic copepods and monogenetic trematodes (flukes) are the primary pests. Although rarely a major concern in the natural environment, they can proliferate to problematic levels in the confines of an aquarium. Fortunately, they can be easily detected and controlled. Initial signs of a problem include vigorous scratching, clouded eyes and reddened patches on the skin.
Even if new arrivals show no sign of infestation, they should be isolated and treated. Three one-hour formalin baths (1 milliliter/gallon) in a separate container, spaced five days apart, are an effective prophylactic. Copper sulfate solution (0.5 ppm for 1 hour only) can also be added to attack latent protozoans. Conspicuous copepods on the fins can be gently removed with forceps. Heavy copepod infestations should be treated with organophosphates (0.65 to 1.0 ppm for 24 to 48 hours), while serious fluke problems will succumb to 10- to 15-minute freshwater baths — watch for signs of excessive stress. It is a good idea to give all fish a freshwater bath just prior to introduction into the main tank. Although copepods and flukes are relatively easy to eradicate during the quarantine phase, these pests are far more difficult to eliminate once established in the main display.
Feeding Temperate Animals
Proper nutrition is a vital component of the successful aquarium. Fortunately, the aquarist with a temperate marine tank is faced with a relatively easy task. Particularly among temperate fishes, the extreme specialist feeders of the coral reefs are generally absent. However, it still important to have adequate knowledge of the feeding habits of all your temperate specimens.
Temperate fishes are generally not fussy in their selection of foods, greedily accepting just about anything that comes their way. Pieces of squid, clam, krill, shrimp, non-oily fish and commercial mixes or any other seafood make an excellent diet, provided a variety is given. It is essential that you ensure the pieces are small enough to be engulfed by all mouths. In the cooler water of the temperate aquarium, appetites tend to be lower than for comparably sized tropical species and you should feed somewhat smaller portions.
The distinctions between grazers, browsers, predators and plankton feeders that exist in the natural habitat tend to break down in the aquarium, but this information can be used as a general guide to feeding habits. Predators, for instance, will tend to present more of a threat to other fish than browsers, who in turn may harm display invertebrates. Knowledge gained from natural history guides and from experience should enable you to gain a thorough understanding of all the feeding styles within your temperate aquarium community.
Live foods are a nutritious delicacy that your fish will relish. Brine shrimp are the standard live fare, but people living near the ocean have a far more delectable source. Swirl a fish net through seaweeds in a tide pool and you should come up with a plentiful bounty of various small shrimp, amphipods and other edible delights. Those with access to a boat can do the same with floating fronds of kelp — hundreds of shrimp-like crustaceans, known as mysids, can easily be collected. Just about any fish, particularly those with small mouths, will become ecstatic at the sight of these juicy snacks.
Feeding invertebrates presents more of a challenge because they exhibit a far greater diversity of feeding styles. Some invertebrates, such as sponges and tunicates, filter tiny plankton particles, while others graze or prey on more substantial items. In general, filter feeders are the most difficult to satisfy in the aquarium and should be avoided in favor of those that select larger foods. Some time should be devoted to learning about the general feeding habits of each invertebrate species you plan on maintaining. This will help to avoid such mishaps as adding large predatory sea stars that will ravage your beds of sessile invertebrates.
In part two I will deal with the animals themselves. There is a wide variety of species that will make good inhabitants for your tank.