Thank you Aquatic Delight and Darkblade. I use pressurized CO2 and have over 100 PAR at the substrate using a LED light system. I read a comment in a thread here saying dwarf hairgrass would not grow in it, or any other ground cover.
I am just in the process of a redesign and wanted to have a ground cover.
After 50 years I do a lot of things right, but still get things wrong