Caring for Fish Tanks during Power Outtages
Battery Powered Air Pumps are Lifesavers
So you're experiencing a major thunderstorm, blizzard, tropical storm, etc. and house is pitch black. How do you care for your fish? Without adequate help, fish will only live for another 24 hours at the most. This is because your filter setup brings vital oxygen into the water, so the fish can breathe. No filter, no water flow, and your fish are left to survive with the amount of oxygen in your tank initially. Unless you keep weather loaches, anabantids (betta, gourami), or a lungfish, you will need to find some way to aerate your water while power is on the way. On the other hand, if you keep weather loaches, anabantids (betta, gourami), or a lungfish (very rare), your fish may survive until power is back. Those fish are known to be able to take in oxygen from the surface of the water.
First, you want to make sure temperatures are stable. Most tropical fish thrive at around 78-82 degrees water. So, without power, your heater is dead. Fish become more skittish and unhealthy at lower temperatures, so you really want to insulate your tank. Cover your tank with styrofoam if you have it, or just use blankets to prevent heat escape. The blankets also help by keeping the tank dark, so your fish don't get spooked or frightened. This is a stressful time for them. Here is where having a bigger tank comes in handy. Smaller tanks are easier to heat up because they have less volume of water, and therefore they loose heat faster than a larger tank. If you have a 10 gallon tank, it will probably get cold in around 10 hours. With a 125 gallon tank, it will take much longer to turn cooler. That is because there is much more volume of water to change temperature.
Once you have your blankets covering your tank, you want to worry about aeration. The BEST method is to use a battery powered air pump. These can be obtained at your local sporting goods store such as Dick's or Modell's. They will have these in the fishing section. Fishermen use battery powered air pumps to keep their bait (minnows usually) alive. Well, in this case it will keep your pet fish alive. Just pop in a D cell battery, and plug the air stone into the airline tubing, and voila, you have an aerater to pump vital oxygen into your tank. This is by far, the safest and best method for keeping oxygen in your tank and keeping your fish alive.
Lets say that you don't have a battery powered airpump, and your car is out of gasoline so you can't make a trip to the store. Well, there are still things you can do, although much more difficult. You can take a large soda bottle (2 Liter), and empty it. Puncture small holes in the bottle via thumbtack or needle. Make sure you do not punch in too many. Fill the bottle with some gravel, or try to tie the bottle to something in the tank so it doesn't float. The little holes will allow air in the bottle to escape, aerating your tank. This method will only last around 10 minutes at the most on average, so you have to keep emptying the water out of your bottle. This works better for small tanks. For very large tanks, a tire can be used. Do the same thing, puncture some small holes in the tire and tether the tire onto something so it doesn't float up.
Hopefully this helps. During a power outtage, the two most important aspects of a fish tank are temperature and oxygen. Longer power outtages (up to a week long) may cause future problems, such as ammonia poisoning. However, for most power outtages that last a day or two, these methods should help keep your fish alive. For me, I have only lost 1 fish out of my 7 fishtanks due to a power outtage.