If its getting shorter your lacking something. ****Does it have dark patches in the leaves. ****Holes? ****Does it look like its deteriorating? ****Is it still healthy? ****I would double the excel dosing for 3-5 days. ****While its a great source of carbon, it doesn't replace CO2. ****How much lighting is over your tank?
Edit:
http://www.plantgeek.net/plantguide_...arch=hairgrass
Good basic info on harigrass
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