I changed the black mesh from 1/4" to 3/4". With the 3/4" mesh I'm now seeing a ~10% reduction in PAR from no top. The 1/4" mesh I was seeing double that (20%). With the 3/4" mesh I'm also not seeing a PUR reduction, which I saw with the 1/4" mesh (2-3%).
Another major change is that I changed from the GHL Mitras to a T5 ATI SunPower with Reef Brite XHO Actinic Blue.
I took readings at a 9" mounting height and obtained the following:
PAR with Reef Brite at 60%: 1/4" = 120-125, 3/4" = 140
PAR with Reef Brite at 70%: 1/4" = 135, 3/4" = 150
PAR with Reef Brite at 80%: 1/4" = 140-145, 3/4" = 158
PAR with Reef Brite at 90%: 1/4" = 150, 3/4" = 165
PAR with Reef Brite at 100%: 1/4" = 150-155, 3/4" = 165
With the Reef Brite at 60% the PAR reduction was 11-14%.
With the Reef Brite at 100% the PAR Reduction was 6-9%.
A couple of observations with the readings.
- I was able to get a more stable PAR reading with the 3/4" mesh.
- The Reef Brite PAR did not really change from 90% to 100%. I'm controlling it with the Reef Brite Apex Dual Channel interface through my P4.
The readings were taken on the sand bed close to center.
The 3/4" mesh is bird netting that I already had from a hardware store.
I would really like to see a more controlled test with clear vs black, different mesh sizes, various power settings and different meters.
The following screen shots are with:
Screen Top: Black Mesh 3/4"
Light: 24" ATI SunPower 4-Bulb (2x Blue Plus, Actinic, Coral Plus) with Reef Brite XHO Actinic Blue, ATI Fixture 12" off water and 11" off screen top
Tank: 24" (L) 18" (W) 18" (D)
At this height the Reef Brite at 100% is giving me ~50PAR.
Reef Brite at 70% Top On
Reef Brite at 70% Top Off
Reef Brite at 0% Top On
Reef Brite at 100% Top On