Safeguarding Your System from Meltdown -
Stopping Murphy in His Tracks: Part I

About once a month I hear about a member of my local reef club having a tank crash. By tank crash I mean an event in which a number of organisms are either lost or significantly harmed. Many of these disasters are serious enough that afterward the reefkeeper is so disillusioned and crushed by the loss that they sell any remaining equipment and livestock, and give up completely. The reefkeeping hobby can be so rewarding that I'm always sorry to see a hobbyist bail out.

A great number of losses can be easily prevented with a little bit of planning and foresight and an understanding of the things most likely to go wrong. It is necessary to carefully consider the value of the organisms that have been collected in a tank, in terms of their dollar amount, their sentimental value and the increased value from coral growth and fish maturation (particularly clownfish that are laying eggs). Estimate this value and then add to this the effort required to obtain all those organisms again and one can quickly see that protecting your investment using the tips I will discuss in the following series of articles, are not too large a price to pay for peace of mind. If you consider all the trips to aquarium shops to find that one unusual color morph, the effort involved in positioning all the corals and perhaps nursing them to a healthy state after acquiring them in a less than ideal condition from a shop, quarantine time for fish, as well as devising the order of fish introduction to minimize fighting and one can see that for a large tank that's been set up for a number of years, the value of the critters in your tank could be measured in thousands, rather than hundreds, of dollars!

Loss of Water Circulation

By far the most common cause of livestock loss, and one which I have suffered though twice, is the loss of water circulation. Depending upon your system's design, once the main circulation pump stops operating, the drop in dissolved oxygen concentration in the tank can be very fast. The rate of this drop depends on many factors, but is greatest at night in a heavily stocked tank with a sand bed. I have nothing against sand beds (I'll leave those arguments to the rabid bare bottom vs. deep sand bed folks), but there is little question that the organisms in the sand bed, at least in its upper layers, consume oxygen, and accelerate the drop in the tank's dissolved oxygen.

I have noticed that the first organisms to succumb to low oxygen levels are usually the large, active fish such as tangs and butterfly fishes. Fish that naturally come from a particularly well-oxygenated part of the reef (Pseudanthias spp., for instance) are also quick to suffer from oxygen depletion. However, fish that are accustomed to living in areas of low current, or where it's laden with detritus, or those that have a lower rate of activity, seem much less susceptible (mandarins and clownfish, for example). Surprisingly enough, I have found that corals, including Acropora and other small-polyped stony corals, are remarkably resistant to short periods (a few hours) of low dissolved oxygen levels. Typically, when circulation is restarted, many corals extend their polyps as if nothing had happened, even those that were exposed to and partially dried by air during the loss of circulation.

A loss-of-current sensing, auto-activating battery powered air pump can supply life-giving oxygen to the tank's inhabitants should a power outage occur. The pump can operate for several days on a fresh pair of batteries.

The loss of circulation can occur for many reasons, but the most common, and the easiest to plan for, is the temporary loss of electric power. Of course the likelihood of power loss varies depending upon where you live, but nowhere that I know of has a zero percent chance of power loss. Several years ago I stumbled across a must-have product, which I now preach that everyone with a fish tank, reef or otherwise, should have: a battery powered air pump that contains internal circuitry to sense the loss of alternating current voltage that then immediately turns on and begins pumping air. With a fresh pair of D-sized alkaline batteries, these pumps can run for several days at full output. When line power is returned, they shut off immediately so that any salt spray is minimized. These pumps are typically priced around $13-$17 U.S. and are, therefore, within anyone's budget. I've found that having one of these pumps for approximately every two feet (.609 m) of tank length is sufficient to keep oxygen levels in a healthy range for all fish and invertebrates in the average tank. I've made my own small acrylic brackets to hang the pump near the top of the tank in the rear, out of sight. Alternatively, the pumps could be located some distance away provided there is not too much back pressure through the tubing running to the tank. The pumps should be attached to a piece of rigid airline tubing. The tubing is run to the tank's very bottom and terminated with an airstone. I typically hide the tubing and the airstone behind the tank's rockwork (all my tanks end up with the "rock wall" look that all the books say you're not supposed to have). An inexpensive plastic check valve should also be installed between the pump and the rigid airline tubing. That, in combination with the air pump's location near the top of the tank's water level, eliminates the possibility of an inadvertent siphon emptying the tank's water onto your living room floor. Surprisingly, I've found that neither the rigid airline tubing nor the airstone becomes plugged by the growth of algae or other organisms, and typically the system can be relied upon to operate properly even after not running for years. Still, testing the system every few months is, of course, advisable as the quality control on these inexpensive pumps might not be as high as on other aquarium equipment.

In the short term, there is little doubt that livestock lost during circulation loss is caused by low dissolved oxygen levels. While the air pump with the airstone will prevent this loss, little water motion is generated with this configuration. I have performed mass transfer experiments in a laboratory that prove conclusively that the transfer rate of oxygen into a body of salt water is much faster with the air flowing out of an airstone than with a simple open-ended piece of rigid tubing. The open-ended pipe configuration will, however, generate more turbulence in the tank than an airstone because the large air bubbles rise much faster. In my experience, most corals are not affected by current loss in the short term, however, one can add an additional emergency air pump ending in an open pipe to generate additional turbulence to maintain the corals' health.

Emergency air pumps are clearly a low-cost insurance policy for your reef tank and can help guard against losses due to a power outage. It is best to plug these air pumps into the same electrical outlet as the main circulation pump (run extension cords or powerstrips, if necessary) so that if, for whatever reason, there is a power loss (overall loss of power to the house, or loss of power only to that outlet as in the case of a ground fault interrupter tripping) the air pumps will be activated.

It is also possible that the loss of recirculation could be due to something other than loss of electricity. In this case the air pumps would not help solve the problem. This particular circumstance also occurred in one of my tanks, causing the death of several large fish. There are a number of reasons that circulation loss can occur without electrical power being lost, but usually in tanks with sumps, if this occurs the water level in the tank itself, not the sump, will fall as water drains back into the sump. If your tank is properly plumbed, the water level will drop only to the level of the overflow or the siphon break. In this case, a powerhead placed near the top of the tank in such a way that a slight decrease in the water level caused by the main circulation pump failing, would allow air to be aspirated into the powerhead, forming a swarm of bubbles that would be distributed throughout the tank, thereby providing sufficient oxygen transfer into the water. It may be necessary to experiment with the proper placement level for such a powerhead, and inserting a piece of tubing into the powerhead's aspirating orifice may help. The tubing can be cut until it is just the right length to allow air to be aspirated when the tank's water level reaches its lowest, but not when the circulation systems are working properly.

Reducing the Risk

I have described how to prepare and safeguard for a circulation loss, but ideally we would like to make the loss of circulation less likely. For those aquarists who use a hang-on-the-tank overflow rather than a drilled tank, the overflow has a significant risk of failure. Overflows can fail from a siphon loss either in their U-shaped tube, or in whatever loop is used to maintain flow out of the tank (CPR style overflows). Siphon loss usually occurs due to bubble accumulation at the U-tube's top or loop. These bubbles can be generated by pumps sucking in air, or bubbles released into the tank from algae mats, sand beds, algal growth in the tubes, etc. As those who have run overflows know, in many cases there is a "sweet spot" for flow rates through an overflow. Too high a flow rate to the tank and the overflow cannot keep up or, in some cases due to the extreme turbulence as water is rushing into the overflow, more bubbles are swept into the U-tubes, which causes siphon loss. With too low a flow rate, bubbles might be swept into the U-tube and not flow out, again resulting in a siphon loss. U-tube siphons can also fail during a short power loss if the U-tube is slightly elevated and the water levels on either side of the tube drop too low, again resulting in a loss of siphon. U-tubes can also become plugged with fish, snails or other invertebrates or debris and therefore it is best to attempt to protect the U-tube from plugging by such critters. I've found that super-gluing plastic cable ties in a cross-pattern over the U-tube's inlet is usually sufficient to protect them from sudden plugging.

Another way to decrease the risk of losing circulation is to use a more reliable main recirculation pump or, ideally, on large systems, to use redundant circulation pumps. I have a closet full of failed submersible pumps from a wide variety of manufacturers. While I'm not saying there are no reliable submersible pumps, I will state that as a class of pumps, they are much less reliable than external pumps. The problem with submersible pumps seems to be that very few of the designs are engineered to properly dissipate heat. In a saltwater environment, a slow precipitation of calcium carbonate occurs in the locally warmer water in the vicinity of the impellor, eventually causing the impellor to seize up. This is most likely to occur just after a power outage, when the pump simply will not restart. Some commonly available, inexpensive and very popular submersible pumps have an even more serious design flaw. When these pumps seize up they continue to draw power and generate heat, and when their plastic case cracks or melts, they can eventually release toxic chemicals into the water, which can cause a near 100% wipeout of the tank. Some hobbyists delude themselves into believing that if they clean their pumps on a regular basis by dissolving the build-up of calcium deposits with acid or vinegar, the problem will never occur. While it is of course true that regular cleaning helps, the pumps with this design flaw are, in reality, ticking time bombs in every tank where they are used.

External pumps are not completely immune to calcium deposits, and for this reason we should be mindful whenever turning them on and off. Many aquarists put their main circulation pumps on feed timers that turn the pumps off for a few minutes while feeding. While this might be a way to minimize the waste from food lost because it ends up in the sump, this benefit must be weighed against the risk of the pump not restarting. External pumps vary in their risk of seizing due to calcium deposit formation, and when searching for a reliable circulation pump, I suggest hobbyists do a bit of research on the brand they are planning to use, or simply pick a brand that has a well-established reliability reputation among hobbyists. There are a multitude of hobbyist's comments on various pump's reliablity, for example, on Reef Central. The bottom line is this, all pumps fail eventually; therefore, it is the prudent aquarist who has a spare, functioning pump at the ready. For extremely valued systems, running two or more circulation pumps is an option that will allow for a pump's failure without the risk of losing your system. There are also flow rate sensors that can be plumbed into a circulation system that will trigger an alarm and/or call a telephone number when it senses a drop in flow rate when used in conjunction with a system controller.

Automatic Top-off Systems

I'm a firm believer in the automation of mundane tank maintenance chores as much as possible. Of course, one of the most common chores required is the addition of freshwater, or kalkwasser (calcium hydroxide solution), to replace daily evaporation. The over-addition of kalkwasser or freshwater is another common tank disaster that I've known to completely wipe out some of my fellow club members' tanks. These over-additions can cause sudden changes in salinity and pH, and can occur due to failures of automated water addition techniques. For kalkwasser additions from a reservoir, it is important to ensure that there is no chance that the addition tube could slip down and accidentally pump a slurry of calcium hydroxide into the tank. Too fast an addition of top-off water can occur when top-off reservoirs are at a higher elevation than the sump or the tank they are being added to, and therefore a siphon forms and adds liquid until the levels have equalized.

In my experience, the safest way to automate top-off addition is to use a peristaltic pump in combination with an inexpensive level detector and a standard lamp timer. A peristaltic pump moves water by forcing it through a section of tubing by squeezing the tubing with a set of moving rollers. These pumps are somewhat more expensive than other devices for pumping small water volumes, but they have the advantage of being able to pump water up or down from a reservoir and into a tank many feet, or even several floors, higher in elevation. This capability of peristaltic pumps makes it possible to have the water top-off reservoir located a significant distance from the tank, which is nice if space is tight in the vicinity of your tank and you want to minimize noise or clutter near the tank. Having a remote water reservoir also may allow the reservoir to be very large to minimize the frequency at which it must be tended to, or to allow enough capacity for the aquarist to be away from the tank for a long stretch of time. Additional advantages of peristaltic pumps include no requirement for priming, no danger of damage should they run dry and little chance of a siphon occurring in either direction when the pump is off. The rollers on the pump act like a valve on the tubing when the pump is off. Peristaltic pumps are not fool-proof, though, and their tubing will wear over time and develop leaks, so it must be inspected and replaced as needed.

I've found the pressure-activated level controllers to be much more reliable than float switches. Float switches are prone to failure due to the formation of deposits on them, or just due to equipment in the sump leaning against them and not allowing them to move up and down freely. I've used the inexpensive pressure-activated level controllers for many years and have never had a failure of any kind. Ideally, the peristaltic pump is plugged into the level controller, and then the level controller is plugged into a timer. The length of time it's on and the peristaltic pump's rate are then set so that in the extremely rare circumstance that the level controller fails in the "on" condition, the pump will be able to pump only slightly more than the required daily amount of top-off water needed. That way, there will be many days to detect the problem, and in the meantime there will be no extreme over-additions of top-off water. Additionally, the timer can be set up so that in the case of kalkwasser additions, they can be spaced out over a larger time period, and they can also be set to occur only at night, thereby minimizing the day/night pH fluctuations that might otherwise occur.

Although perhaps not as convenient, the safest way to reduce risk is to use a smaller freshwater reservoir, so that in the worst case, even if all the systems fail and the entire volume is added, it is still not enough to change the tank's salinity (or pH, if pumping kalkwasser) enough to cause significant damage to the tank's organisms.

Uninterruptible Power Supply (UPS)

We've already discussed the electrical current sensing air pumps that can maintain dissolved oxygen levels during a power outage, but there is another option - connect the main circulation pump to some type of uninterruptible power supply (UPS). Uninterruptible power supply systems capable of powering a circulation pump can be expensive, so such a system should be carefully evaluated in comparison to the value of the tank's inhabitants. As a rule of thumb, I would recommend that a hobbyist add up the value of the tank's livestock and consider investing at least 5-10% of that amount in UPS equipment. Uninterruptible power supply units designed for computer equipment may work for this purpose, but generally they are not suited for the type of power draw that is required for a tank. Computer UPSs are designed for supplying power for only a short duration, under a relatively large power draw, while the UPS for a reef tank backup would ideally be able to operate at a slightly lower power draw, but for much longer time periods.

There is currently a device on the market (shown below) that combines a power inverter (DC to AC), a trickle battery charger and an auto-switching relay that senses AC power loss. This device can be easily wired to a bank of deep-cycle marine batteries linked in parallel and can deliver power for a considerable period of time depending upon the pump's power draw and whatever other equipment is plugged in. I set up one of these devices with a pair of marine batteries and found it could run a Gen-X Mak-4 pump for more than 16 hours at normal, full-speed operation; long enough to make it through most power outages. These UPS systems transfer power immediately upon the loss of AC line voltage, with the equipment never skipping a beat. When AC power is restored, the marine batteries begin to recharge, and the equipment running on the UPS automatically switches back to line voltage. There are even adjustable tolerances for the "quality" of line voltage required before the equipment switches back to line voltage.

I have my battery-powered air pumps also plugged into the marine battery UPS system, so that they will not kick on until the UPS is depleted. This will minimize any salt spray that might otherwise occur. If a UPS with a lower reserve capacity (i.e., fewer marine batteries) is used, the aquarist could alternatively plug in a powerhead that might aspirate air when the tank's water level drops, and circulate air bubbles about the tank. Small powerheads are likely to have a lower power draw than a main circulation pump. Ideally, it is best not to drive tank heaters or chillers with a UPS, as comparatively, they have a very large current draw and might not even operate properly on a UPS. In most tanks, a short-term cooling is not likely to significantly affect the occupant's health, and such cooling will actually make low oxygen levels less likely as oxygen is more soluble in cool salt water. If you have to make it through a really long power outage during cold weather, the tank can be heated by floating bags or plastic bottles of hot water. The water could be heated in any number of ways (e.g., propane stove, Sterno, fireplace, etc.) that do not require electrical current.

The choice of which piece of equipment to run on a UPS will, of course, depend upon the configuration of your particular aquarium. As we have discussed earlier, low dissolved oxygen levels are most likely to be the cause of livestock loss during a power outage, so whatever piece of equipment is most likely to keep dissolved oxygen levels up is the equipment that should be kept running. In tanks with sumps and overflows, sufficient water aeration occurs as the oxygen rich water at the surface is drawn off and circulated to the rest of the tank. Also, in most tanks, as this water runs over the overflow, additional air is entrained and mixed with this water as it falls to the sump. In tanks without sumps, a HOT (hang-on-the-tank) protein skimmer might be the best piece of equipment to keep operating in case of a power outage.

Those who have a lot to lose and who live in an area that is particularly prone to power outages, may want to consider having an automatically-activated propane or liquid fuel-powered generator wired to their most critical pieces of tank equipment. Such systems can run into the thousands of dollars to purchase and set up, but might buy considerable peace of mind for those extended vacations to Fiji.

Part II in this series shall cover temperature control and emergency notification equipment, and will describe a range of miscellaneous problems that Murphy is looking to trip you up with.