Recently, I didn't heed my own advice on having a fish tank. I didn't have back-up equipment that could have saved me a lot of trouble.
I had checked the temperature on my 55 gallon display tank one morning to find that there wasn't even a reading on the thermometer. The temperature had dropped so low, it was below that of the 68-degree low range reading. In fact, it had dropped to probably in the low 60s. For a tropical tank that is usually kept at 74 - 78, this could be quite a problem.
The source of the problem was a faulty heater. No matter what I tried, it wouldn't work. And who knows how long it had been out, since I hadn't checked the temp in a couple of days.
Now on to an emergency trip to the pet store...who didn't have the size heater I needed!! So, on to the next store who did have one on the shelf.
I was lucky...I didn't lose any fish in the long run. But for a $22 heater, I should have had one in reserve, even a used one, to insure my overall investment of fish. With fish tanks, one little error such as this could cause major fish loss.
The thing that saved me, I think, is that the temperature dropped slowly and I'm guessing the heater probably wasn't broken for that long. Fish are more sensitive to sudden temperature changes then they are to a more gradual change. Which is why it was important when I got the new heater to only increase the temperature by a few degrees ever 4 hours over the course of several days. I also added some ich preventative, since when fish are stressed out, they are more prone to disease.
I'm happy to report that all the fish are fine (and warm), but that I could have saved myself some time and aggravation by having a back-up.