If you use bleach in an aquarium, you can't leave it there for too long because it breaks down the silicon (glue that holds the glass together). Bleach can be wiped over the inside of the glass tank but should only be left for 5-15 minutes, then rinsed out well with tap water. When it no longer smells of bleach, fill the tank with water and leave it for 24 hours, then drain and refill it. Set it back up.
Granulated swimming pool chlorine is safer to use and does the same job. Take the tank outside and put it in the shade on a flat level surface. Fill it with tap water and add some pool chlorine (see directions on packet). Leave it for an hour or so and then drain and rinse the tank under tap water. When it no longer smells of chlorine, fill it with tap water and leave it overnight, then drain it and set it back up.
Liquid household bleach is sodium hypochlorite.
Granulated swimming pool chlorine is calcium hypochlorite
NB. If you use bleach, do it outside or in a well ventilated area.
Wear safety glasses, rubber gloves and if possible, a plastic apron and face shield so you don't get any on your skin. The apron and face shield aren't normally necessary but can be used for added safety.
NB. When bleaching an aquarium, monitor the silicon and if it starts to go white, wash the tank out with tap water immediately.
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You can also use white vinegar and soak the glass and items with that. Vinegar is an acid and won't affect the silicon. It's also a lot safer for people. You wipe everything down with vinegar and leave it for 24 hours, then rinse off with tap water. Leave it to dry for 24-48 hours and set it back up.
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Drying out an aquarium and accessories will also kill most things that live in water. Having the items outside in the sunlight for a few hours will also kill things.
NB. Be careful if you put the glass aquarium out in the sun because they can sometimes crack if they get really hot. This is more likely to occur if you have the tank sitting on the ground.