Normally you just wash the tank out with water and let it dry for a few days and this will kill most aquatic disease organisms.
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You can use soap to wash the tank out and rinse it well, then let it dry. Use a soap that does not have any perfumes in.
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You can fill the tank with clean water and add lots of salt. Have enough salt so it no longer dissolves. Let the filter and everything run for 24 hours and then drain and wash everything and let it dry.
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You can use alcohol (70%) and wash everything with it. Leave it to dry. If using alcohol in hot climates you should wash the tank and equipment several times and try to do it in a cool area so the alcohol has 20-30 seconds to kill everything.
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You can use bleach (liquid household bleach or granulated swimming pool chlorine) to disinfect the tank if it had fish tuberculosis or the gourami Iridovirus in. If you use household bleach, use it straight and wash everything with bleach. Leave it for 5 minutes and then rinse it out really well.
If you use granulated swimming pool chlorine, fill the tank with freshwater and add some granulated chlorine. Let the filter run for a few hours and then drain everything and wash it with fresh water.
*NB* Chlorine granules or liquid bleach should be used outdoors because the fumes are poisonous and can kill people, birds, animals, reptiles, fish and even insects.
*NB* You should wear rubber gloves and safety glasses when working with bleach/ chlorine and avoid getting it on your skin or in your eyes, and don't ingest it or inhale the fumes.
Warning about bleach/ chlorine and silicon. Bleach/ chlorine will damage silicon over time. The stronger the bleach concentration and or the longer the bleach is in contact with the silicon, the more damage it does to the silicon. This is why it should only be left in contact for 5 minutes and then washed off really well.
