Tank wiped out - mystery solved

Since you are talking about temperature, I wanted to add something about heaters.

One catastrophic problem that can occur is that the heater thermometer can break. If it breaks, it can either be off all the time or on all the time. One should keep on eye on the heater, especially during fall and spring. The reason is that, unlike the summer/winter when your home/appartment is either cold or hot, the changing seasons cause the thermometer to turn on and off a lot. This can lead to wear and this is the time of year they tend to break.

Thanks for sharing. So few people do this. I wish more of us would share our mistakes. I think it would help other a lot.

I have made my own 'thought a parameter was OK' only to find out differently error (salinity)

Agree... it is hard to believe a reef tank can reach 18'C with all the water movement devices adding to the heat... Not even mentioning the lights during day.

Plus you would feel the colder water when you reached in the tank for any reason.

Good advice. I've heard of a few cases of catastrophic failure of a heater basically killing off a tank.

My approach is to use at least to small heaters instead of one larger one. They are both set at about tha same temperature. If one fails to turn on, the other will at least maintain the temperature at a lower than optimal setting until I get a chance to replace it. If it fails by remaining on, the lower power makes it more difficult for the water temperature to climb dangerously.

I find most people use heaters that are too large. 300W may sound impressive and therefore better than a 100W, but if the 100W is all that is needed to maintain the temperature in a tank that is sitting in a heated room, do you really need the extra power and the risk that goes with it?

Not too mention that the 100W will gradually increase the temp whereas the 300 W is quicker and tends to overshoot.