I think the substrate is fine. I like bright colors. Which is why I like freshwater plants and fish.
With the HOB with the Bio-wheel have you considered replacing the O2 in the bubbler with DIY CO2? (airline hose, 2 soda bottles, bread yeast, sugar, baking soda, etc.)
So long as you always have the filter on, the CO2 should do great for both the plants and the fish. Just an idea.