Steve,
I agree that you have a moderately lit or even low-light tank despite the 3+ watts/gallon. You can either change things to get more light in the tank or start treating the tank like a low light tank.
Three things come to mind for increasing the light; 1) lower the fixture, 2) build a "wall" around the top of the tank to reflect light back into the tank and 3) convert the light fixture to use t8 lamps.
I can understant why you wouldn't want to lower the lights or build the "wall". Both moves would damage the open-topped aspect of the tank. It looks to me like the lights in your fixture now are about shoulder-to-shoulder, which means that most of the light from the top half of the lamps is restriking the lamps instead of going down to the water. The light you get going downward may be as little as half of the light that the lamps are producing. A big part of the light that does go down is spilling outside the tank. The rest is being converted to waste heat. T8 lamps will give you about 1/2" more space between lamps where light from the top of the lamps can be reflected down to the water. There will also be less waste heat from the ballast and less waste from the fixture.
Carlos' comments on over-running the demands of the tank are about right. I recently decided that CO2 and fertilizer on two low and moderately lit tanks was doing more harm than good. I stopped treating them like high-light tanks; algae is hugely reduced, no plants were lost, plants are growing well and the tanks are both more pleasant to look at and easier to care for. I made the change in three steps First I shut off the CO2, then I stopped macro fertilizers, then I stopped trace fertilizers. I'm in the process now of returning some of the fertilizers to a level appropriate for the tank. First I found (and it didn't take long) that I needed to go back to trace fertilizers. Now it looks like I'll need to add some potassium, which I will do as KCl
Roger Miller |