Hello; Over the years I have avoided metal whenever possible for my tanks. Back a few decades ago stainless steel was common for some aquarium equipment. I think there are reasons I do no use metal pots even stainless if decent plastic buckets are available.
I seem to recall this is a brackish setup. If my memory is correct then the salts are a bit more likely to react with metal than fresh water.
Correct me if I am taking your comments wrong. Are you saying you use the same metal pots for the tanks and other things such as cooking and cleaning?
I have been careful about chemicals around my tanks. Not sure what such non-toxic cleaners you speak of but even with such things I have a set of buckets and tools such as sponges only used around my tanks. I have another set of buckets and tools used around the house and never around or for my tanks.
What about someone putting something in a tank?