The aquarium death spiral is a situation where an action is taken to fix a perceived problem, but that action actually makes the situation worse.
Most commonly, the Death Spiral happens when an aquarist doses an aquarium with antibiotics, anti-fungal, or anti-microbial medications. The medication has the unexpected effect of killing off the bacteria that comprise the bio filter, which results in an uncycled tank. The situation quickly beings to deteriorate, since an already sick fish is now exposed to the additional stress of ammonia poisoning.
Another common situation occurs in goldfish bowls. After adding a goldfish to a bowl, the fish becomes lethargic and may stop eating. The owner sometimes interprets this behavior as loneliness, and adds a second or third fish. The original problem was, in fact, not loneliness, but rather the effects of ammonia poisoning. Adding additional fish dramatically increases the amount of ammonia present in the water, and soon the fish are dead or visibly dying.
