Would using soap to clean a goldfishes fish tank kill it?

Using regular cleaning products meant for household tasks is hazardous for fish. Soap would be especially harmful as it removes the slime layer that protects fish from the external environment and can cause a skin infection on the fish. Fish can also accidentally swallow soap bubbles which can block their digestive tracts. When this happens, the soap bubbles act as a laxative that passes too quickly through the digestive tract and inhibits it from absorbing nutrients from food. Additionally, leftover soap suds can remain on gravel, plants or ornaments inside the tank, which the fish may come into contact with again.

When cleaning a fish tank, one must ensure they are using suitable equipment and products made specifically for aquariums. For example, a mild bleach and freshwater mix will disinfect the tank and plants without harming the inhabitants.