Hairgrass is rather easy, I've produced nice thick clean lawns for over a decade now.
CO2 is the main issue. I've done well with plain sand and RFUG's, Kitty litter and sand, ADA AS, Flourite etc.
It's not picky about the sediment.
You may need more light. 1.5-2w/gal is a good range for most folks.
CO2 is a huge issues and many think using low light means no CO2 is required which is true, but you gain a great deal in adding with low light tanks without nearly the hassles you deal with in hgher light tanks.
2.2 w/gal using PC's or T5's is fine.
You are a bit on the lower side, but even there, many folks have grown plants fairly well using PC/T5's with CO2.
Reagrds,
Tom Barr