Go Ahead and take everything, Obviously if anything looks knackered throw it away. But What I do/ have done in the past is soak everything in a non-scented bleach, In the UK I use Milton fluid it is just bleach (sodium hyperchlorite and salt) which is safe for children and used for milk bottles for babies ect.
So everything is scrubbed first, using a sponge/ scouring pad and a non-scented soap.
I then fill the tank with water, and add the correct dilution of bleach, soak everything inside the tank for a few days. Everything is then rinsed several times to remove the bleach (fill tank fully with water and drain several times).
First, never use filter media, substrate, wood or rock from another aquarium. These items can absorb/adsorb pathogens and there is no effective way to ensure they are killed or removed. And any substances like bleach should never be used on these as the bleach can remain and leech out later.
Disagree Byron, bleach is widely used in the Aquaculture industry worldwide as an effective disinfectant on everything from nets to entire tanks and pipework. So is UV light, lime and hypersaline solutions (for FW at least).
However there needs to be two steps to cleaning everything in a tank, Cleaning and disinfection. You are right, products like bleach on their own will not get rid of everything, but that is not what they are designed to do. You need to scrub everything with a soap (non-scented) to remove the grime and the bio-film, RINSE. Then you can disinfect effectively.
Rinsing the full volume of a container 3 times is considered good enough for oceanographers who are concerned about contaminants from soaps and cleaners, simply rinsing effectively will remove any bleach left on any equipment. Plus bleach degrades easily in water as it is just a sodium salt of an alkaline solution.
