I love having a large fish tank in my living room for a number of reasons, but it’s a lot of work. The fish are beautiful and relaxing to watch, especially if you experience chronic anxiety like I do. But the enjoyment I get from the fish has to be offset by the labor that it requires to care for them on a weekly basis. Feeding the fish is the least of my worries. It’s carefully removing them from the tank without harming them or stressing them out, combined with the effort needed to drain the tank, clean off the algae thoroughly, and then refill it with water before putting the fish back. If you don’t clean the algae consistently, it creates a musty odor in the house that smells like moldy pond water. And if the odor is left long enough without getting cleaned, it starts to permeate the entire house. That’s why I thought my fish tank was dirty the other day when I noticed a gross odor in the house. I was ready to clean my tank when I realized something important. The odor appeared after I turned on my electric furnace for the first time in eight months. I forgot that it was normal for the furnace to smell bad after it is unused for months at a time. Everything from dust to microbial growth settles on the heating coil while the a/c runs during the rest of the year. When it’s turned on for the first time after resting for a while, it has a nasty odor until the buildup is burnt away.