Bacopa is large for a stem plant. I have that and the fish wont eat that or the one I used to have that was the golden Bacopa. Bacopa is the Arnold of stem plants.
With plants it takes patience not the fast growth people imagine plants will do in low tech. Moving them around is one setback after another if not a killer. Java ferns take months to build up a root system to grow on.
If you want them to fill in an area fast? Then don't buy one,buy a whole group of them. That's the fastest way.