On a gallon basis, bleach is the chemical I have used the most of in relation to tanks for the past 13 years. It has many uses but it must be used properly.
There are a few things to understand. First, only use plain unscented bleach.
For pre-treating most new plants or for removing algae from mst existing plants, use a 1 to 19 mix- bleach to water. Dip most plants for 90 seconds, rinse well and drop into a bucket with a good dose of dechlor. Very fine leaved plants may not survive dipping. So test a small piece if you are unsure. Not all algae will appear dead immediately, do not worry about this and don't over dip the 90 second limit.
For cleaning the micron carts for the Magnum line of canisters, its a 25% bleach solution over night. Rinse well and do not reuse until they dry out 100%. This is what Marineland suggests and I have been doing for a lot of years on multiple HOT Magnums.
For cleaning used tanks, the more you can use up to about a 10% solution works fine. Its a cost issue, Cleaning a 150 gal tank would take a lot of bleach. The bleach should sit in the tank for about an hour. This should kill about anything. Rinse the tank out a few times and then allow it to dry 100%. (I then may use a weak hydrochloric acid mix to get the white stains out- this is more dangerous than bleach.)
I use a 10-15% solution to sterilize any reusable items from a hospital tank as well. I put everything into the H tank, then fill it up with water and add in bleach and let it all soak a few hours. Sponges do not do well in bleach, so I normally throw them out.
I do not like to bleach wood going into a tank. It absorbs water, and thus bleach as well. The bleach will discolor the wood and then drying it out can take a long time. Keep bleach away from carbon- you do not want to see the mess it makes.
Finally, I bleach clean hoses. Short ones I do by holding them ends up level and pouring in bleach slowly. this has to sit a bit- either hold it or clip it upright so the ends stay level. Longer ones I hook to a pump in a bucket of bleach mix and just put the output end into the bucket and let the pump run a while. Again rinse well and if you are worried, circulate a dechlor mix through the hose after the rinse.
Never get bleach into tanks, it is for cleaning/dipping things away from occupied tanks. It also should be handled with care as splashing in on your clothes will trash them and you do not want it in your eyes or mouth. Remember, bleach is chlorine.
I am not a fan of bleaching sand, its too much work to rinse it and to have it dry out completely. It can be done, however.