OK, water parameters prior to a water change:
KH 17.9 (1 drop on API test)
GH 125.3 (7 drops)
Not sure how the nitrates got that high, assume there was a lot of ammonia processed with not enough plants to use it up. I'll take care of it with some water changes.
A bit concerned about KH. Not sure if I need to do something with that to have healthy shrimp and snails or not. Guess I have some reading I need to do. Maybe a post in the invert subforum.
EDIT: What about getting some Fluval Mineral Supplement
If I go with Nerite snails, how many would be good for a 9 gallon tank? I know they're smallish. 5? 10?