It is important to balance light intensity with other nutrients. Intense lighting will be wasted if not enough CO 2 and nutrients are available to support the needs for photosynthesis. This is very important to plant growth. Some plants do not need much CO 2 and some plants like Cryptocorynes actually seem to do worse with higher levels of CO 2 . Most plants will flourish with levels of 10-20 ppm but this requires some type of CO 2 injection.
Ammonium is the preferred source since it takes less energy to use that form of nitrogen.
A good test for ammonium levels is to monitor nitrates. If the nitrates are 0 ppm, you know that all the nitrogen is being used. This may indicate that some plants are starving for nitrogen. It also might indicate that a perfect balance has been achieved, but that is unlikely. Unfortunately, potassium is difficult to measure in the water.