good, I'm glad you read the article. I don't think your fishies will react badly to it. In my experience, snails move so slowly and mind their own business that fish don't even know they're there. (Unless they're snail-eaters and then they notice quickly!)
One ramshorn will work just fine, especially since they are hermaphrodites, so any two snails you put together will breed (e.g. everybody is the "opposite" sex, since they all have both sets of organs). Ramshorns (and most freshwater snails I think) are peaceful. While there are some marine snails that will harpoon and eat fishes, those available for FW aquaria will not.
Just keep in mind, though, that if the ramshorn you purchase happens to be "pregnant", it may lay eggs when it's in your tank. In which case, you may end up with tons of baby snails. The article gives ways to control their population, though, like not overfeeding and keeping up with tank cleaning/water changes.
Sorry if I scared you earlier. Lately there has been a lot of verbal abuse, to the point of name-calling, on this forum. We got 2 new moderators today, so I think it will get better.
Thanks for taking my advice! Let us know if you have any other questions
