Weeping moss grow rate.

Ok when I ordered my shrimp I got some narrow leaf java fern. Mixed in with the roots was a little bit of weeping moss. I have ben able to put about a dime sized amount (flat) on a rock. Does this moss grow quick? I have 2 wats per gallon on for 8 hours aday. (going to upgrade to 4wpg after jan.) I was wondering how long it will take to get this to grow say to cover a 10gal. Tank bottem. What do you all think it will take?

Thank you. I have it tied to a rock right now. Oh and thanks for the moss John it made my day. Shrimp are doing good and active. I think I have lost 2 but they may have just shed becouse it was hollow shells and I check on them every hour or two durring the daytime.