With my acrylic tank, I used plastic razor blades and a Mag-Float magnetic algae cleaner with an acrylic-safe scrubbing pads. They cost somewhere between $7-10 and you can purchase both the scrubbing pads and plastic razor blades at
Aquarium Cleaning Products . In my opinion, you have plenty of rock but it's all about what you like. Good luck with the tank, looks like you're off to a great start!