This is an interesting thread. I was under the suspicion that my lack of CO2 use in my 15 gallon long was causing my HC to disappear, but based on this, it may be my lighting. I am using a Coralife NO T5 (28 watts), Eco-complete, and Excel along with EI dosing. From a significant swathe of HC, I'm now down to 2 patches, but they are very low growing and appear to be healthy. Maybe it's time I though about more light.
Filstar pimp #59 (shhhh on the Eheim)