Which is a greater danger, cold or heat? MUST KNOW.

[Sk8r]

Heat.
Your tank temp is around 78-79.
Lethal cold starts around 62 degrees F.
Lethal heat starts around 85 F.

If you have a heater failure, don't panic. Turn off fans which cool the water. YOu can float chemical handwarming packs (hunters use them) in tight Ziplocs if you have to, but if the chill looks to be a typical 3-8 hour power failure, no sweat. In a longer one, wrapping your tank in a blanket or insulation, even styrofoam, may help retard the loss of heat.

If you have an overheat, first thing is turn off your lights and set a powerful fan to running on your water surface. A fan is good for a 10 degree drop on a 50 gallon tank. You can also float ice cubes in a Ziploc. LIGHTS OFF BECAUSE: 1. corals and coralline can start bleaching at 85 especially if the lights are on, making them biologicially 'awake'. If lights are off it protects them. 2. lights also contribute a lot of heat to a tank.

Remember that HEAT is a state of energy, but COLD is the simple absence of heat. So to protect from heat, you have to stop the energy (turn off the lights, yes, but NEVER the pump!) and get it to lose some, as in exposure to ice. TO protect from cold, you have to prevent heat from flowing away, which is why insulation can help.

Remember that hot water can't carry las much oxygen as cold water. This poses an added danger. Increasing flow helps a tank cool down. A fan does too. And if you suspect the water is oxygen-short, putting a bubbler in is not a bad move, but keep it away from fish and corals.

And lastly, remember that water heats and cools rapidly: rock and sand retain heat or chill long after the water has gone to the other state. Your corals tuck down against the rock or inside stony skeleton for self protection; your fish tuck up against a warm rock. So even if your water has hit a disaster-edge 62, your fish may be ok, down in the warm rocks. Don't despair. Start remediation asap.