I have a freshwater aquarium that has been set up for approximately 1 year. During routine cleaning and water change I found baby snails everywhere and on everything, even in the back of my tank. I haven't added anything new to the tank except a few shrimp since I set it up so I have no idea where they came from or how they ended up in my tank. I have fish, shrimp, a Betta,2 mystery snails (my male just died) a nerite snail, Cory cats and plants. These have literally came out of nowhere and I'm at a loss. Never seen an adult of any kind in my tank the entire year. Help? Thanks so much