Pond snails are not a bad thing. Pond snails will only reproduce to the point of the food they can eat. So if you get overeloaded with pond snails your over feeding. I did a test in my fry tanks when was last empty. Set up 3 10g US tanks. Added 10 pond snails to each tank. All same plants same lights, and no filter.
Tank 1 Didn't feed tank all snails crawled out of tank and made a run for it. Did 20% pwc every 3rd day
Tank 2 Light feeding once a day. Had small incress in amount of snails. Did 20% pwc every 3rd day.
Tank 3 Heavy feeding. Whent to way to many to count in a matter of 3 weeks. Did 20% pwc every 3rd day. At first water was not up to par but to keep it a true test did not change anything. Even thoe toward end of test, tank there was not alot of left over food in tank.
I have on avg 10 pond snails, 10 trumpet snails, and 3 mystery snails, in my 55g tank. Never seem to find lots of pond snail eggs. Never had mystery snail eggs. (could all be same sex thoe). Trumpet snails have not mutlipled that I can see but they are new.
I keep lots of pond snails in my fry tanks, not real good looking but are good at cleaning up after the fry.
Clown loach is still eating good, after the test.