Bleach is one of the safest and most effective methods of sanitizing an aquarium prior to initial setup. Many aquarium hobbyists are afraid to use bleach because they fear its potency. However, bleach is perfectly safe if used correctly. We use bleach for disinfection because it is one of the most effective chemicals we have for disinfecting. It is commonly used in US hospitals and is recommended by the Center for Disease Control. Bleach, or sodium hypochlorite (NaClO), is also safe for the environment. It breaks down very quickly, leaving behind mostly salt and water. Because it is a strong disinfectant that quickly breaks down into harmless byproducts, it can be used to disinfect baby and pet toys, aquariums, and is even used to disinfect our water supply.
When purchasing bleach to clean an aquarium, use only regular bleach such as Chlorox Regular Bleach or equivalent. Do not use bleach mixed with detergent. Detergents leave behind dangerous residues that can be fatal to aquarium fish.
Using typical household bleach (which is typically already 5% bleach), mix 9 parts water with 1 part regular bottled bleach in a container. I like to store it short-term in a spray bottle purchased at my local hardware store. Keep in mind that bleach breaks down pretty quickly, so only make small amounts at a time. Never store bleach in a bottle that has been previously used with other chemicals.
Here are six simple steps to sanitizing your aquarium with bleach.
1. Clean any debris from the aquarium with warm water and a paper towel.
2. Spray all surfaces of the aquarium with the 10% solution you have just prepared. I like to do this in my bathtub to contain overspray. Outdoor sanitizing is also a good option.
3. After spraying all surfaces, let the aquarium sit for 10-15 minutes. Bleach is a corrosive chemical and can cause damage to your aquarium if left too long. Do not let it sit for more than 15 minutes.
4. Rinse well. When you are done rinsing your tank, rinse again just in case.
5. Let the aquarium air dry completely. This will help ensure that the bleach solution has broken down into harmless byproducts.
6. Once you set up your aquarium, fill the tank with water and dose with a good aquarium water dechlorinator.
Aquarium gravel, decorations, filters, and heaters can also be bleached using the same concentration of bleach water. You can spray them or soak them in a container depending on what you are cleaning. Be sure to rinse all bleached items very well and allow everything to air dry completely before placing them back in the aquarium. Keep in mind that metal rusts quickly when exposed to bleach. As mentioned above, never allow the bleach to sit on the item for more than 10-15 minutes, and keep an eye on metal items especially.
IMPORTANT SAFETY INFORMATION:
Bleach can be very dangerous if inhaled or ingested. May cause moderate to severe damage if in contact with eyes or skin. It can also cause discoloration or corrosion of some materials. Review the safety information on the bottle of bleach before handling it.