beautiful tank, hate to see you give up the scape because the plants grow too quickly. Have you tried cutting back on the amount of lights, perhaps just use 2 of the CF lights or just use the MH by themselves?

Some options for grass like plants are:

Sagittaria
Blyxa japonica
Blyxa aubertii
Eleocharis vivipara
Eleocharis acicularis
Cyperus helferi