I just bought a light that claims to output 330 PAR from 20" away (in the air of course)- I plan to hang it closer to 10" away, so using the inverse square law I can probably expect around 1320 PAR. I know that natural sunlight at the surface of the ocean can reach around 1500 PAR, so I'm not too worried about killing the chaeto. However, I do want to know, in the case that I have to lower the light, if the chaeto will suffer. I've read people saying they have grown chaeto under sunlight supplemented by 3 metal halide bulbs, so I can't imagine that overlighting is an issue with chaeto. What is the highest PAR (Estimated or measured) that you've grown your chaeto at?