Planted Tank Enthusiast
Join Date: May 2019
Location: Palm Springs, CA
+1 for the Hygrophila difformis & Sunset. Just got some H. pinnatifida & balasamica, so will be interested to see if they grow as quickly.
Hornwort planted in the substrate can grow to the surface in 2-3 days, but quickly loses its lower leaves in medium light, so isn't a desirable stem plant long term. I use it as a nutrient sponge in new tanks to prevent algae blooms, and it's great for hiding fry.
Water sprite is another extremely fast grower.
Not technically a stem plant, but jungle val can quickly cover the surface with leaves 3'-4' long, and put out runners that will take over the entire tank if you don't keep on top of it.
Should we have a contest to what grows fastest?