my first plants moss ball,and dwarf hairgrass!!!

mehopes you have some good lighting, i've never had dwarf hairgrass survive in anything less than moderate to strong lighting.

good luck though. Read Rex Grigg's website, it's chock full of questions and answers.

What kind of lighting do you have?

If it was a 29 gallon tank with std. fluorescents, then you're looking at about ~40 watts for the total light above the tank. It's possible the purplish glow is from plant lights. Could you look at the bulbs when they're turned off and tell us any names/writing you see on them?

Assuming you have a 29 gallon, you roughly have 1-1.5 wpg. That's not enough to support the hairgrass. =( sorry

I'm not certain about the moss balls, but they may need high light like the hairgrass as well.

No, the moss balls should be good. The like cool temps and can survive under very low light. One guy said he kept one in a fridge for several years in a cup of water when he got it from japan and forgot about it. When he discovered it in the back of the fridge, it had split into two more balls and the original ball had grown bigger as well.

http://www.kokosgoldfish.com/MossBalls.html
http://en.wikipedia.org/wiki/Cladophora

I find that the hairgrass in my tank is pretty dormant under 2wpg. At 3wpg it really thrives. It is a slow spreader and takes time to fill in to a total carpet.

Agreed, I have had a small patch of hairgrass with 2.4 wpg and it has barely grown in 6 months.