Barrel heaters are usually used by concrete contractors to keep their concrete from freezing, drying out and cracking. However, barrel heaters can have other applications. Fish hatcheries, for example, rely on heated tanks to hatch eggs and grow little fish into bigger fish before they are released back into the wild. Hatchery farming raises "domesticated" fish for food. In the event that your tank heaters fail, you can use a barrel heater in the following ways.
Fish Barrels and Heaters
Keep some concrete mixing barrels in storage for emergencies. When your hatchery heaters fail, you can take a barrel out of storage in which to put your fish. The temperature in the current hatchery tank should last just long enough to heat the mixing barrel with a wrap-around, blanket style barrel heater. Until you can replace the broken or malfunctioning hatchery heater, your fish eggs or young fish should be quite comfortable in the barrel. You can set the barrel heater temperature to the same temperature as your hatchery tank so that the eggs or fish are not shocked by any temperature shifts during their transfer to the barrel.
You May Need More Than One Barrel and One Heater
Because of the limited space inside a steel drum barrel, you may need more than one to hold all of the little fish or medium-sized fish you have to transfer. You do not want to cause the fish any distress by overcrowding them in one barrel. It can lead to starvation and death as the fish struggle to swim about and get enough air, so place them sparsely inside the heated barrels. Conversely, your fish eggs, as long as they are not due to hatch for some time, can practically fill a barrel and be quite fine by themselves.
Transporting and Releasing Fish from Your Emergency Barrels
In the event that you have to conduct an emergency transfer of fish from a tank into a heated barrel and those fish only have a few days left before their release into the wild, you can keep them in the barrel until then. You could even transport the fish in the heated barrel to the release site, and gradually reduce the drum heater's temperature to match the water temperature in the release zone. In the final half hour prior to release, the barrel temperature should be exactly the temperature of the water into which the fish will be released, which you can check and adjust by arriving at the release site ahead of time.