Here's a note about Excel...
Tom Barr (PlantBrain) suggested I dose Excel at a level of 5ml/10gal daily. Yes, daily! Now, I have a pretty heavily planted tank, but my growth has exploded!!! He doesn't recommend going any higher, but my 55 gal is proof that at 5ml/10gal, it works great.
I'd build up to that amount though.
Oh, and I use metracide 14 and adjust by 60% of the Excel dose.