Same here. My tank don't have high light.I've found hydro Japan only grows horizontally for me if it's getting enough co2 round the lower levels of the tank, otherwise it tends to grow tall and leggy IME.
YepIt's a superfish 60ltr tank with the built in LEDs.
Do you mean NOT getting enough CO2?
It'll grow tied to rocks or tied to wood, you could trim off the long stems and keep pressing the rest down to keep it looking compact, grows so quick though this can become more work than you want.OK, I might pull it out and tie it down on a rock. Is that a good idea, or does it need to go in the substrate?