valuable information than the demonstration that brine shrimp can be killed by a particular pump. It is true that additional experimentation is needed (Adey and Loveland, 1991), though we wish to emphasize that the concerns about pumps killing plankton are not so important for reef aquarium systems. Furthermore, alternative pumping systems such as diaphragm and screw pumps have four disadvantages: high cost, large size, noise, and frequent need for service or repair (Adey and Loveland, 1991). The difficulty keeping such organisms as sponges, bryozoans, hydroids, filter-feeding clams, or non-photosynthetic corals will not be solved by switching to these pumps. Difficulties with these organisms can be overcome by: the scale of the system (i.e. really big closed ecosystems can produce sufficient plankton to support filter-feeders); the use of refugia as described earlier or; by the addition of cultured plankton for small systems. It lias been repeatedly demonstrated that plankton is not necessary for growing photosynthetic stony corals (see Carlson, 1987 and Teh, 1974). In addition, some filter feeders may suffer not from the lack of plankton, but from shortage of trace elements used for metabolic functions or to build their tissues (see chapter 8).
On the subject of pumps, the failure of water circulating pumps or air pumps is an event that you can count on happening eventually. For this reason we recommend duplication of these items. If you have a natural system aquarium run by airstone only, use two air pumps, and replace the diaphragms periodically. For systems that use water circulating pumps, there should also be redundancy of pumps as a safeguard, and a bubbler in the tank provides still more safety. Even when water pumps are regularly cleaned and serviced, failure can occur. An additional spare pump kept packed in the closet may come in handy too, in the unlikely event that both pumps should fail, or for replacement parts.
Submersible pumps offer flexibility and freedom from plumbing, but some caution about their tise is worth noting, in addition to our comments earlier in this chapter. Submersible pumps use the water to dissipate heat, so they tend to raise the temperature of the water. This effect is of most concern in small aquariums. In large aquariums, the temperature increase is slight. Some submersible pumps are filled with oil, and could pollute the tank if a leak in the pump casing developed. Likewise, a leak in the pump casing
could result in electrical current in the aquarium. Saltwater and electricity are a deadly combination. This potentially very dangerous situation is made less dangerous by the use of a ground fault protection device, available from hardware stores.
Battery backup can provide short term continuous power supply to run the aquarium pumps in the event of a power failure. Battery backup systems have been available for years for computers, and are now becoming available for aquariums. The high density of life in reef aquariums rapidly consumes the oxygen from the water in the event of a power failure, particularly in a dark room. Battery backup can offer hours of air pumping or water pumping, depending on the system, and the batteries are recharged when the power comes back on. Long-term power failure from hurricanes, earthquakes or other natural disasters requires the use of a generator to supply power to run the pumps and chiller (if necessary). Your investment in a reef tank probably justifies the purchase of a small, gas-powered generator for emergencies .
Good plumbing for aquariums combines art and science. The best plumbing, however, is no plumbing at all. The simplest, worry free aquariums have no holes drilled in them, and no pipes that could leak or need cleaning. In practice, most tanks have at least some plumbing, but we wish to make the point that the less plumbing used the better. We have all seen plumbing jobs that looked like so many upset intestines.
To achieve the best pumping efficiency, it is best to avoid 90° turns in the plumbing. We have seen physically elegant plumbing jobs installed with many PVC elbows to keep the plumbing flush with the cabinet. While this may conceal the pipes nicely, all of those hard turns reduce the flow of water to nothing compared with the actual pump output. Smooth curves are better achieved with flexible PVC, or with hose barb fittings and flexible hose or tygon tubing. Likewise, avoid sharp turns on the intake between the sump and the return pump. It is best to maintain a straight path.
Llse wide pipe diameters for drains, to allow unrestricted flow and good venting of air trapped by the draining water. Small diameter drain pipe limits the maximum flow or size of the recirculating pump, and increases the chance of a blockage that could cause the aquarium to overflow and spill water onto the floor. Wide pipe diameters should also be used on the intake side of recirculating pumps to maximize throughput.
Aquarists often use check valves in the plumbing to prevent back-flow of water from the aquarium to the sump. We advise all aquarists to design the plumbing so that check valves are not needed. Check valves are not failure proof. They do fail eventually, and the result can be disastrous. Several types of failure can happen. The most common type of check valve failure is called "hammer". It occurs when the water running back down the pipe compresses slightly against the closing check valve, and then pulls it back open with the recoil. A hammering "thunk-ka-thunk-ka-thunk-ka" sound is characteristic. The valve is working with each "thunk", and failing with each "kaallowing a little water to pass down each time. If there were infinite water above the valve, this would be a perpetual motion device! The w ater drains down until the power comes back on. A long power failure when the aquarist is away from home could mean an empty tank, a wet carpet, and possibly some astonished downstairs neighbors. Another type of failure with the same awful result occurs because of the growth of sponges, calcareous tube worms, or just accumulation of slime or calcium deposits on the ball, flap, or seat of the valve. These cause irregularity of the valve surfaces, and prevent it from making a complete seal when the power goes off. Growths may even hold the ball or flap in the open position. Aquarists generally use check valves to allow for the installation of bottom jets or water returns below the surface. Bottom jets are not really desirable, and returns below the water surface should be near enough to the top that the water draining down with a power failure can be safely contained within the sump. The size of the sump should be designed to contain all water that drains down when the power is off.
The location of probes (electrodes) and holders can affect the accuracy of readings and the ease of maintenance of the probes. Probes should not be located where light will cause algae to grow on them. Algae and growths of bacteria (bio-film) or sessile invertebrates will make readings inaccurate. If the probe is located in a relatively still pocket of water, the reading may not reflect the values in the majority of the aquarium. If a probe is installed in such a way that it cannot easily be removed for cleaning and calibration, then it is unlikely to be maintained properly. Locating probes in the reservoir in a region where there is gentle flow of water and relatively high w^ater exchange, provides accurate readings, a shady environment, and an easy place from which to remove them for cleaning and calibration. A special, small dedicated probe holding reservoir can also be used. A "tee" fitting with a special probe-holding end allows neat installation in-line
A practical design for an in-line sampling station for the location of probes (ie. pH, redox, temperature). Water is pumped into the containter at the bottom and overflows into a standpipe drain at the top. Photographed behind the scenes at the Bochum Tierpark in Germany. J. Sprung.
with the plumbing, but does not allow easy maintenance, and the high velocity of the water in the pipe tends to increase the deposition of a bio-film on the probe tip.
The plumbing may require periodic cleaning in reef aquariums, because of the growth of marinelife that coats the inner surfaces (see appendix B). Clear pipe or hose in brightly illuminated locations should be avoided because it will quickly become clogged with algae. When clear flexible hose or pipe is used, black electrical tape or other shading material can be placed over it in the most illuminated spots to prevent algae growth. For opaque pipe, it is wise to install union fittings and valves that allow the plumbing to be completely disassembled for cleaning. Such cleaning may be necessary about once every two years. Make the section lengths short enough to pass a foxtail brush through.
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