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.
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
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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