Tropical Fish Hobbyist

Letters to the Editor

Backup for a Power Outage

In the May 2009 issue’s “Freshwater Q&A,” you suggested using an uninterruptible power supply (UPS) to provide power during a power outage. This is not necessarily good advice, at least not in the simple way it was presented. Most low-cost computer UPS units do not produce sine-wave power when they switch to battery backup, but square-wave (stepped) power. This is good enough to operate electronic equipment, but it is not suitable at all for electromagnetic equipment such as filters or air pumps. Those devices will not operate during a power outage when connected to a low-cost UPS, and they may be damaged beyond repair.

There are UPS units that produce true sine-wave power, but they are much more expensive (usually more expensive than a small generator). These are the only UPS units that should be used for an aquarium setup.

Technically speaking, heaters can run on a low-cost UPS, but only for a few minutes. This is totally pointless— if the power outage is short, the heat capacity of the water is enough to maintain water temperature, and if the outage is long, the extra few minutes won’t do any good. Moreover, if the UPS power is drained by the heater, it will stop supplying power to the pumps (assuming that a sine-wave UPS is being used, of course).

For those who own multiple and/or large aquariums, a small generator is the only viable solution. It usually costs much less than replacing the livestock, not to mention the moral issues. The problem with a generator is that you have to be around to power it up and connect it in the case of a power outage (generators with an automatic starter and switch have ridiculous price tags). This is true for the low-tech blanket method also, by the way.

My solution was to retrofit an inexpensive battery-operated home alarm system equipped with a dialer to page me on a power outage (basically this involved using a small relay for a detector). My aquariums can run without power for the time it takes me to drive back home and connect the generator.

I believe that owning delicate livestock bears some responsibility, and the cost of supplying good power

during a power outage should be taken into account. Amiram Stark

Tel-Aviv, Israel

Dear Amiram,

First, thank you very much for writing and pointing out the potential confusion from our response. We should have elaborated our answer. You are quite right that UPS devices that are sold primarily as computer power backups should not be used to power aquarium equipment during a power outage, and that more costly UPS devices that produce true— not simulated—sine-wave power can provide short-term backup, but for the same money you can have a generator of much greater capacity that can provide continuous backup power.

Of course, the original question in the May issue involved a 5-gallon tank that cooled off rapidly. Since, as you point out, devices like aquarium heaters will quickly deplete most battery backup devices, a generator would be a much better choice. Most people, however, would regard a generator as backup for a 5-gallon setup as overkill. There are deep-cycle battery systems that could work, but again those are a bit much for a 5-gallon setup. As we pointed out, an insulating blanket or a foam board enclosure for the aquarium would retain the heat if applied immediately when the electricity goes out. One could even take a cue from fish shippers and set a small cooler with a heat pack taped inside over the tank. The suggested battery-powered air pump could provide circulation and filtration.

Today many aquarists, especially reefkeepers, are investigating UPS devices as backups, and your reminder serves to redirect them to generators rather than battery backups, which were never meant to replace a normal power source for an extended period. Since generally the only power failures to concern aquarists are long-term outages, and since electricity-hogging heating, lighting, and cooling are at least as important as circulation, it makes sense to pass on any type of battery backups, even if they produce the correct form of electricity. Investing in a backup generator instead, as you correctly point out, is really the most sensible option if your setup cannot withstand an extended power outage.

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