I have a 20gal high, medium light. I think I have eco complete topped with black sand. I put in HC 2months ago. I use root tabs. No CO2 until recently. It was going well, very easy to grow. It was not growing fast, but I knew it would eventually cover.
About three weeks ago I started up with DIY CO2. The HC has at least double in size in that amount of time. I think that the entire bottom of my tank will be covered before the end of May.