Hair grass or Eleocharis acicularis (also called as 'Needle Spike-rush') is one of the most difficult species that I have handled. As the name suggests (Hair Grass), this is a grass-like plant with very fine leaves resembling human hair. This is low height plant that requires high light and nutrient rich substrate and forms a dense underwater 'lawn', making it quite popular among the aquarists, as a 'foreground' plant. It does really well with regular CO2 supply and fertilization.
Hair grass, is found as a bunch of thin threads, entangled with each other. The toughest job is to plant them. Hair grass does extremely well if individual plants are separated in smaller clumps and each clumps are planted in the substrate, separately with a pair of tweezers. Once planted, do not forget to clip the tips off, after a week or two. Hair grass is also very prone to be affected by brush algae. Clipping the tips regularly, helps to control the brush algae growth on the thin leaves of hair grass. Once, the thick 'carpet' is formed, remember to vaccum regularly to get rid of the debris, deposited in the dense 'carpet' of hair grass.