Blankets and Styrofoam sheets will help conserve tank heat during the winter months.  I suggest you get Styrofoam sheets used in home insulation.  These sheets are easy to cut to size to match your exact needs.  I suggest one sheet for all four sizes and one for the bottom.  If your hood can be removed easily, one for the top may be a good idea as well.  These Styrofoam sheets are easy to attach to the tank with masking tape and can be stored out of the way in the garage or attic until needed.   Most homes have a few extra blankets or comforters that can be tossed on top of the tank.  Nothing too fancy, the more the better.

Battery-powered air pumps can be very cost effect ways for providing aeration and water current to your tanks.  I happen to have the Penn-Plax “Silent Air” Model B11 which uses two D batteries.  It can typically be purchased for about $11-15 on-line.  This unit has a very useful feature: it will not turn on until it detects the AC power has gone out.  If you’re expecting a storm in the night or perhaps expecting a storm and you have to leave the house for some reason, it is very easy to add one or two of these to your tank.  If the power does not go out they never turn on.  But if it does go out and you are not around, they will buy you some time until you can get your plan in place.  I would suggest using a minimum of at least one unit for every 2 feet of tank length for most standard tank sizes.

When using battery-powered air pumps (or even normal AC air pumps on a UPS unit) don’t use an air stone or wood block.  Simply run the tubing to the bottom of the tank.  Rigid airline tubing works best but standard airline can be used.  In either case you may need to add weight to the hose to keep it in place.  I use a rubber band to attach the hose to my cleaning magnets and drag the magnet to place it where needed.   The large rolling air bubbles will create surprisingly good current and water surface agitation for gas exchange. I’ve found large rolling bubbles to be much more effective than the fine mist of bubbles produced by stones or wood blocks.

The Penn-Plax “Silent Air” Model B11 unit that I have uses two D size batteries.  The unit will also run on a single battery but will obviously not run as long. In my tests running the unit on two D batteries the Model B11 unit last just short of 5 days of continuous use.  I was very impressed with this.   A unit like this is a must-have for every person with an aquarium.

DC/AC power converters (sometimes called “invertors”) are inexpensive and flexible devices often overlooked by reef hobbyist.  Converters that will power 400 W (watts) of devices can typically be had for $35 on eBay.com web site.  These devices can be hooked up to an extra car battery or better yet marine batteries used on boats or even directly to a car via a cigarette lighter port if you can park within an extension cord distance.   These are ideal for running a heater and a powerhead or two.  It can also be used for recharging a mid-sized UPS unit if you can’t get the car close enough to the tank.  DC/AC power converters are really your only cost effective way for running a heater.  Typical aquarium sized heaters in the 100-300 W range will drain just about any UPS unit in a matter of minutes. Obviously, a generator would be ideal but they are priced beyond the reach of many hobbyists and tend to be in short supply when you really need one.   If you do hookup a DC/AC power converter to a running car be smart about it:  put the parking break on, do not run the car in the garage (deadly fumes) and make sure nobody drives off with your car.

The DC/AC converter also comes in handy for non-reef related items such as road trips and camp outs.  My 400 W converter was plenty for running a small TV and a DVD player for my daughter.

The unit I use runs cool to the touch, is very quiet, can easily be converted from cigarette lighter to battery terminal feed.  It has a 20 A (ampere) fuse with two power outlets and a master on/off switch.  The unit weighs less than a pound.  I’m really impressed with it.

Uninterruptible Power Supplies (UPS) and generators are pricey items.  In most cases a generator will be recommended over a UPS.   A UPS is typically used for computer systems to protect them from sudden power outages.  Most people have fairly small UPS units designed to run the computer for only a few minutes – just long enough to power down the system safely.   These smaller UPS units will likely be a waste of money for most aquarium hobbyist.   Larger (and expensive) UPS units may have some use in the hobby.  However the costs are in the same area as entry level generators which make it hard to recommend them.  If you happen to have one handy use it. If generators are not an option based on where you live then perhaps a large UPS unit in conjunction with a DC/AC converter is your best option. 

Another drawback of a UPS unit is battery life, not only in terms of how long it will last when the power goes out but how long the batteries will last before they need to be replaced.  It is common for batteries to need to be replaced after 5 years of use.  It may be less expensive to purchase a new unit instead of replacing the batteries.  This is yet another reason to consider a generator instead.  

In selecting a UPS unit you should know a few facts.  There are two main types of UPS units: on-line and near-line (also called line-interactive).  With on-line units your equipment is always running off the battery and the battery is always being charged.  Near-line UPS units run the equipment from standard household electricity and switch over to battery only when the power spikes to high or drops to low.  Many near-line units can provide some filtering of the power without switching over to battery.  For example, my UPS unit will deliver acceptable voltage to appliances plugged into it when the line voltage is between 103 to 130 volts.  A house with ideal current will run at 115 volts but fluctuations between 110 and 120 volts are common.  On-line UPS units effectively filter input power and provide a constant power source (see side bar “How do on-line UPS’s work?)  but have reduced battery life.  These are great features for sensitive equipment, not really needed for power heads and air pumps.   Weight can be a serious issue for some of these units.  My 3000 VA unit weighs in at just under 180 pounds.  I have it on a board with casters so I can move it around.   Noise and heat can also be (minor) issues with UPS units.  The inverters can be nosy and generate a bit of heat if keep in a small enclosed space, such as a walk-in-closet.

While preparing this article I tested several UPS units ranging in size from 450 VA to 3000 VA.  I tested them running a MaxiJet 1000 power head (20 W) and then retested with a Whisper 600 air pump (3 W.)   I fully expected to find a decent sized yet affordable UPS the people might consider using.  After looking at the cost versus how long the units were running, I decided to stop the testing.  No UPS unit could be recommended after I saw the Penn-Plax “Silent Air” battery powered air pump last nearly 5 days.  Even the largest UPS unit I tested could not run an AC-powered air pump half as long.  

Generators are the best all-around option for long-term power outage survival.  Like anything, generators have a large number of trade offs that need to be considered before selecting a unit.

In selecting a generator, the most important thing to determine is what capacity generator you need.  There is nothing worse then buying a generator only to discover during a real emergency that your generator is under-sized.  James A. Fox wrote an excellent article (http://www.advancedaquarist.com/issues/mar2002/short.htm ) that covered how to calculate the electrical costs of running a reef tank.  In that article, James shows how to determine the current needed to operate your tank.   This would be an excellent start in determining how large a generator you need for full-bore, business-as-usual operation of the system.  In a time of crisis, the tank might be able to survive with somewhat less power than usual.  For example, your corals will live for a few days under reduced light output. Also, please remember that in a time of power outage, you way want to run other important electrically powered equipment in your house as well.  Many modern heating systems are absolutely dependent on AC power to deliver heat to your house.  You may decide that eating food is nearly as important to you as your reef aquarium, so budget adequate power to run refrigerators, freezers and appliances used for cooking. 

One also needs to keep in mind that generators need to be serviced and tested at least monthly (weekly would be better).  You should run the unit for at least 30 minutes and cut over a few appliances to make sure everything works as expected.  It is not uncommon to have a power outage on a dark stormy night only to find out you are out of fuel.  After getting some fuel from the garage you find out the starting battery is not charged (if you have an electrical start).   If you have a manual recoil start (pull string) hopefully it decided to start up on the first try.  Otherwise it will be like the old lawn mower, weed whacker or chain saw… pull, pull, pull, pull, ouch… my back hurts. 

The next major item to consider with a generator is the fuel source.  You have basically four options: gasoline, diesel, natural gas or propane.  Each one has tradeoffs to consider.  (See table below).  In most cases gasoline powered generators will be your best option.

The location of a generator is a great concern.  It would be very unwise to attempt to run a generator from your basement.  All internal combustion engines produce carbon monoxide (CO) gas.   The CO gas can leak out of the engine exhaust system into your house. The fact that a generator is likely being used during bad weather when your home will be sealed up tight makes it suicidal to run a generator improvisationlly placed in your basement. It is unfortunately not at all uncommon to hear about people requiring hospitalization or dying from CO poisoning from running a generator in their basement.  If the basement is your only option, seek out advice from a local fire inspector to see what building codes you may need to consider.  The technical requirements are similar to putting a hot water heater or boiler in your basement.  Noise and heat can also be concerns with a generator.

If you plan on hooking up any sensitive electronics to a generator be sure to use a U.L.  listed surge suppressor .  Many generators generate power clean enough for power tools and other construction tools but the voltage variations can cause damage to voltage sensitive appliances such as computers, TV, entertainment systems, etc.  Always use a surge protector.

Fighting off a power outage during the winter months is about as difficult as outages can get.  Besides the loss of power you typically lose your household heating.  Not only is this an issue to your family but it is a serious issue to your aquarium.  Luckily you and your family can put on sweaters or jackets for a few hours if needed. The aquarium on the other hand it’s not so easy.  It will be unlikely that you can maintain tank temperature higher than about 15-20°F above ambient room temperatures.  Most reef keepers use a temperature range of 78-84°F.  You should be able to maintain this temperature range with a typical aquarium heater and DC/AC power inverter provided you can keep the ambient room temperature above 60°F. 

As soon as you lose power during the winter months, I would suggest that you immediately try to conserve tank temperature by moving heaters from the sump to the display tank, provided you have at least a DC/AC inverter and a few battery-powered air pumps.  Use at least one air pump per two feet of tank length. (They are sufficiently inexpensive that you can use more than this.)  Once the heaters and air pumps are in place the best way to conserve temperature is by using foam insulation sheets (thicker is better), which can be found at most home improvement centers.  Use one sheet for each side of glass, and ideally one for the bottom and top of the tank too.  Then cover with blankets and towels.  This will be about the most you can do.  Sit back and hope for the best.  Monitor the tank temperature every 30 minutes or so. 

If the tank temperature drops below 72°F you are seriously pushing the limits of many critters in your tank.  If you have access to a gas stove, heat water and use 2 liter soda bottles.  In a pinch you might consider heating tank water itself and slowly pouring it back in.  Even if you’re one of the lucky few with a generator, you will likely still face issues with falling tank temperatures due to falling room temperature.