Originally Posted by Frolicsome_Flora

How are you measuring the CO2? If your using the KH - PH relationship, then your CO2 is more likely in the range of 5 - 20 ppm, which just wont be enough with that much light. You really need to be using a drop checker, as its the most accurate way we have of measuring CO2 content. You want to be aiming for 25-40 ppm CO2, or your going to run into problems.

Which flourish are you using? I would seriously recommend reading up about the Estimative Index method, and using that to dose the tank. Then you could alter that to cater for the black water going into your tank, Tom would be the best to advise you as to how to do this.

Root tabs are always going to help, but with good EI most water column feeders are going to be more than happy with it. EI will lead you to far less issues, less maintenance, and enable you to throw away all the test kits, as theyre, for the most part.. useless.