I had ONE snail, and I had 3 fish w/ it. now my fish are dead, but now I have tons of little snails! how did this happen???
Many snails do not require another snail to reproduce. You dont say if you had any live plants. Many live plants have eggs on them when you get them that you may not notice. As to why your fish died the presence of snails multiplying doesnt really equal a reason for your fish to die nor does a fish dying equal reproducing snails so... that one will require more information.