I'm not sure how you come up with that conclusion. I have a few mystery snails in my fancy goldfish tank and they are fine.Goldfish are very messy fish. Snails thrive on excess nutriants. Sorry but the two organisms just can't exist in the same environment.
What life sustaining nutrients do filters remove?I came to that conclusion because goldfish require clean water especially fancy goldfish. Clean sustainable water can only be created using a strong filter. Strong filters eliminate the nutriants that snails require to survive. Plus snails would have trouble compeating food with goldfish.
Thoughts on placing a snail with goldfish? I've read mixed reviews online. I have 4 total, 3 are around 2in and the Oranda is about 4-5in (size of a fist)