So far as I can tell there's nothing. If you're in Nashua, you could try Textile Aquarium in Lowell. Its worth making a call before you go down there, since he keeps really strange hours. I don't remember the shop having a lot of plants but it isn't generic and has very healthy fish.
I assume you've tried Family Pet and Aquarium (?) off of Exit 7, near Market Basket. They are quite small and not fish-specific, but they had some plants last time I was there.