E. acicularis is tall, around 5-6".
E. parvula is short, under 2" usually.
E. sp. "Belem" is even shorter, 1.5" and curls downwards under higher lighting than E. parvula. Difficult to come by and only available from other hobbyists. Expensive.
I prefer the look of E. parvula since it stays upright and only curls slightly. It grows 1.5" in my tank so there isn't much difference from "Belem".
how do you keep parvula short? lots of trimming? or is more a matter of light? I have e. parvula and I let it grow and it gets to be about 4-5 inches tall. I've only recently started to mow it more frequently.