I have three nerites in my tank, and they like to lay eggs all over the back of my driftwood. Everything I have read says the same thing. They cannot hatch unless they are in brackish water. Are you sure they are not miniature ramshorn snails? They look like this http://4.bp.blogspot.com/_kQ8tSzsH7g...

I have a koralia nano 240 in my 29gallon tank, and it does a fantastic job. I have it placed so that most of the flow is hitting the back glass. This way it doesn't bend any plants, and still circulates water around the tank.