I noticed that one of my tanks had some white stuff in it a few weeks ago and i thought it might be some kind of mold or somthing. So i asked my dad what he tought it might be, and he said that it was just some calcium deposets.

Also all the fish who have lived in that tank have gotten finn rot and died from it

. I resently got a new fish to replace the one that passed away and I dont want him to have the same problems as the other ones so I cleaned out the fish tank really well. (kinda gettin of topic now) So anyway I'm worried that the calicum deposets (or what ever it is) might be harming my fish in some way. So a way to get rid of it (says my dad) is to soak the tank in vinagur. I would like to know if I can use that on my tank, because I know i can't use soap.
If you have a thory on what the white stuff is I would be delighted to hear it.