Just wanna chime in here for my first post as I'm a noob too and I've been running a Fluval Edge 6g too!
I'm using a mix of Fluval plant stratum and Up Aqua Shrimp sand. I'm glad I got the shrimp sand because the fluval plant statum is pretty big and light, you're going to have a hard time getting your HC to stay put. I have to be very careful filling up the tank or the HC will just go loose and float up. You'll want to use something better / finer / heavier than Fluval plant stratum. You'll also want to get a set of forceps to really get the HC down into the stratum (You'll have a hard time with just your fingers).
I haven't had much luck with HC. My first batch pretty much withered up and died. I got a second batch, added a CO2 + diffusor set up and flourish root tabs, it seemed to be okay but after a few weeks it started browning. It's been a week since I've started dosing fertilizers and it looks like things are starting to look better (greener / new buds) but there's not any spread yet.
I've been doing water changes with distilled water (that might be the problem), started doing a half distilled half tap mix. But aside from that, the only thing I haven't really tried is a better light source.