i have a 5 gallon betta tank that i bought new and cycled 6 months ago. at the time, i bought new gravel, plastic plants, it came with an aquatech brand filter & filter pads (all new). it has been setup and running all this time with no problems. about a month to six weeks ago i bought 2 mystery snails, one for each of my betta tanks, but one of the bettas attacked his snail. so the 2 mystery snails wound up in one tank together with the other betta. that was about 4-6 weeks (estimate) ago. everything i read says if they do happen to mate, they will lay an egg sack above he water line & also its very obvious. since i change and inspect this tank once a week, and didnt notice any sign of an egg sack, im assuming this is not a mystery snail. besides, its a dead ringer for the pond snail pics i've seen online. i found it in the top of the ug filter tube near where the bubbles come out the holes. my ug filter tube doesn't have any carbon cartridge attatched. also, this tank has never had any live plants in it, and i have seperate nets/supplies for each of my tanks. how did this lone pond snail wind up in this tank? i should also mention that there were many pond snails in the mystery snail tank at the pet store. i believe its unlikely that snails of one species could produce offspring of a diff. species, right? could a pond snail egg have hitched a ride in on one of the mystery snail's shells? also, none of the water from the store tank inside the bag actually went in my tank either. there was only one snail, so should i be worried about finding more in there? as soon as i found it, it was seperated immediately into a mason jar. can we put this snail in our pond? thanks ahead for any advice.