It's always nice to have an empty fish tank clean and ready for whatever critter may need housing. Cleaning an empty fish tank is relatively easy, though it may take a little elbow grease. Since the fish tank in this case is already empty, some of the hard work has been done. Roll up your sleeves, gather the supplies, and let's clean an empty fish tank.
Rinse the empty fish tank with warm or hot water first, to loosen the soil. If the fish tank is small enough, hold it upside down over a double sink, you can balance the tank on the middle divider of the sink. Use the sprayer attachment to spray hot water up into the fish tank, forcing the soil out into the sink. If it is a large fish tank, use a new spray bottle of hot water to wet the inside.
Loosen as much soil as possible with algae scrub pad and water. Continue to scrub until the glass is clean, take a break and come back if you need to.
If the empty fish tank is not going to be a fish aquarium any longer, use a small amount of rubbing alcohol on the glass inside and out. Rubbing alcohol is cheap and evaporates quickly, use in a well-ventilated area with no open flames or sparks.
Completely rinse the empty fish tank until the water runs clear of any soap bubbles or debris. Wipe the tank out and rinse it well again to remove any leftover residue. Wipe the aquarium completely dry with paper towels.
Mix 1 capful of bleach in a 32oz. spray bottle, spray lightly inside on all sides of the empty fish tank. Wipe the fish tank completely dry with paper towels.
Let glass aquariums stand in the sun for several hours after bleaching. The sun will bake out any residue from the chlorine as well as lightening any stubborn stains that could not be removed by scrubbing.
Save a used fish tank, even if the glass is cracked. Empty fish tanks can be used as homes for other small animals or reptiles. As long as the crack is not too severe or near the bottom, small animals may chew at low lying cracks. Always use a new spray bottle for clean water to be sure that nothing has tainted the interior of the bottle. Rinse well with hot water before using the bottle for fish tank cleaning. Alway use cleaning supplies labelled aquarium safe for the clean tank to house fish in the future.
Do not overbleach, wipe dry immediately, let stand in direct sunlight for up to 8 hours after bleaching. If the fish tank is plastic, don't use abrasive cleaners or tools as they will leave scratches. Certain cleaners will fog plastic making it impossible to see through, others can even melt plastic; chose cleaners carefully. Never put fish in a tank that has housed a small animal.