[summerboy1958]

I have a 30 long with a coral life freshwater light. It has the stock bulbs. My tank is low tech. The chart in the sticky by Hoppy indicates that I have about 35 PAR now. I would like to start using peat to lower the pH, but not remove the tannins (the tank is a SA Apisto and I would like the "black water" effect). Any idea of the reduction in PAR? I have no way of knowing what the concentration will be, so this may be an impossible question.

 

[GeToChKn]

I highly doubt it will affect the penetrating effect of the light. It may look a bit more dim to our eyes, but that doesn't mean it will affect the light itself. Perception and actual are way different. Just take a 2700k cool white bulb or a 6700k daylight bulb. Both will grow plants the same but the 2700k will look yellow and dim and the 6700k bright and white, but to the plants, they don't care.