C Hing what is your light's output and how large is your tank? For Glossostigma, you need at least 3 watt per gallon to make it grow like a grass land, for smaller tanks (say less than 10 gallon), the light to tank size ratio requirement is even higher...and a lot of CO2 is needed too...
I was lucky to have good result with 200 watts of light on 66 gallon...that makes 3 watt per gallon....and I used quite a bit of CO2 too...1 bubble per second at least....