My mistake. It souded like you just stopped giving them any kind of plants.
And you raise a sore point with me: the markup on aquarium plants is nuts!
I have ponds near my house where, if you were diligent and made a real professional operation out of it, you could make several thousand dollars a year just by collecting, washing, and batching horsetails, elodea, and other plants that people buy in the stores.
Yes, I understand that the really special stuff, like Brazilian swordplants and others, are raised professionally and take a lot of time and work.
But elodea does not. Figure out the right requirements, set up a greenhouse full of tanks, and elodea grows... well, like a weed! I’ve had it take over aquariums where I didn’t want it to.
And then stores charge an arm and a leg for a bunch of plants. Somebody—the store, the middleman, somebody—is making a killing on them.
I know that that’s a facile way of putting it, but let me say this: there are a bunch of potential live-plant customers out there who have chosen to not pay that kind of money for plants. That’s one of the factors behind the lifelike-plant industry (and they’re getting better at it all the time).