If the wattage of the bulbs is the normal amount for 36 inch bulbs - 39 watts each - then you will definitely be able to grow hairgrass. It's actually one of the easier carpeting plants to grow, since I myself am growing it in 2 wpg
And yet we ran planted tanks for years using wpg.WPG means nothing, just an FYI, because its more about PAR
but with the light you have, you totally got the ability to grow hairgrass