spend a few hundred on a quality co2 system..its worth it. The diy co2 really doesn't work well. You also should use a quality substrate like eco complete. It, over time will provide adequate nutrients to your plants roots, where the nutrients need to be, as opposed to the water column. As we know, increased phospates in water column combined with nitrates and light equals algal blooms. RODI will keep water column free from phosphates and nitrates but plants still need them for growth. A good quality substrate will provide these for them.