Many plants, such as water lilies and some bamboo, grow well in standing water. However, potted plants filled with standing water can become foul-smelling and fill with bacteria, which is unsuitable for the plants. Bacteria can hinder a plant's ability to absorb water. By adding a small amount of bleach to the water, you can help eliminate the bacteria.
Empty the pots of the standing water, especially if it is foul-smelling or discolored. It's best to start with fresh water. If possible, do this outdoors or in a utility sink.
Scrub the pots--inside and out--with soapy water and a nylon scrub brush. This will help kill remaining bacteria residue. Use an old toothbrush to get under the rims if necessary. One gallon of warm water with a couple drops of dish detergent will suffice.
Rinse the pots well and fill them with clean, fresh water.
Mix in 2 drops of liquid household bleach (labeled 5.25 percent sodium hypochlorite) to every quart of water. Use a dropper for accuracy. Do not use bleach mixed with soap.
Add plants to the pots filled with water. The standing water should not grow bacteria again.