You must never use wheelie bins as filters, as thay are made of
reconstituted plastic, which will kill your fish with the chemical they use for
If you are making your own filter using a large container, make sure it's fish safe. Can you store drinking water in it? Has it been used for food like a orange juice or milk container? These range from 200- 2000 litres, and most are made of plastic.
You cannot paint wheelie bins with g4 to coat them - this DOES not work.
Never use galvanized steel only stainless.
If you buy a so called second hand container make sure you get in writing on a bill head that it was used for drinking water or food transport. I have found many so called fish-safe, and bought as such. The problem is, I cannot save the fish when the internal organs have been poisoned, and death is very slow - starts with fin rot then ulcers. In fact it would pass for k.h.v - and this has happened more than once.
You have been warned!