Duckhams' 75G Reef Build - Eurobraced/BeanAnimal

[Myka]

Originally Posted by Duckhams

A lot of PAR is above the 400 range in my mind too, now that you say it. But I am impressed with the Radion XR15PRO's and the PAR output, especially at 100%, they are powerful little fixture. The addition of a 4th may be necessary as I fill in the tank and things start growing in. I certainly would like to have MORE PAR available, but the real question is, is it needed? My SPS all seem very happy, have good colour, acceptable growth and don't seem short of light. Coral placement is a little more important given there are some lower PAR areas in the back of the tank, but I dont see that as an issue right now. Maybe a T5 or two would bump PAR, growth and colour better than a 4th Radion?

I have to say I do like the PAR range you're getting with the Radions + (only) 2 T5s regardless of the possible err on the measurements. That range is pretty close to what I'm getting from my 36" ATI 6-bulb dimmable T5 fixture.

Is high PAR needed? Well, that depends. First, not every tank is the same, and for reasons that we as a reefing community don't seem to fully understand, some tanks require more or less PAR to achieve the same thing. My guess is that flow, nutrition in the water column, and parameters have a lot to do with it. There are a lot of variables even in tanks that we think are essentially very similar. Do you need PAR over 400 (or 550) in a mixed reef? That's probably not a good idea because more LPS would be bleached by that amount of light. If you have a dedicated SPS tank then maybe you do "need" that much PAR. I've seen SPS tanks in the 550-700 μmol m-2 s-1 and SPS tanks in the 250-350 μmol m-2 s-1 range that essentially produced the same thing - a beautiful, colorful SPS tank.

I never like to feel like I am being limited by my light fixture though. I'm running my fixture right now only at 100% blues, and 60% whites. For whatever reason (flow? nutrition? parametes? or?), I am not able to increase the intensity of the lighting and achieve better results.