FWIW, the E. parvula in my tank tops out at about three inches (or a bit under) so far. It's been in the tank for about two months, and is about 19" from my 2wpg fixtures. Fresh from the pots it was about 1.5 inches. Also, it is really slow to spread, at least so far in my tank (substrate related? (normal aquarium gravel)) so if you're looking for a quick carpet you may want to buy a lot.