Steve,
You definitely are not maintaining a high light system. Although your 6 40 watt tubes may come out to 3.2 wpg, the lack of efficient reflectors and hanging of the lighting 9.5 inches from the surface really cuts back down on light.
Your plants need more light, if the bottoms of those plant species are melting away at that planting density. I would address this issue first.
I would raise the CO2 level to 30 ppm.
As a moderately lit system, I believe you are overloading the aquarium with unnecessary fertilizers. The tank is simply not capable of absorbing all that plant food, and most of it is going down the drain at each water change. I would cut back on how much you dose by half, but do it gradually. Let the tank adjust.
Would you be able to dose for consistency? The algae you describe are, IME, signs of instability. I would split it from two times a week to four times a week.
Let us know how it all works out in the end,
Carlos |