I have been thinking about how plants grow in my tank. I keep a low intensity near the substrate, around 40-50 micromols PAR. I get nice slow growth on plants, get content with that, but as the plants grow taller, they reach the much higher light intensity higher in the tank, and grow faster. Then as they get higher still, they take off like they are in a high light tank. This has to be common, since you can't have a low light intensity all the way from substrate to water level, unless your light is several feet above the tank.
This H.c.Kompakt may be a plant that if kept pruned down below the high light height in the tank, may remain as a slow growing, low plant. If I ever try it, and I almost certainly will, I think I will try that. This may also be why "carpet" plants can suddenly fill the whole bottom half of the tank. Light is so tricky at times.