T5 Lighting: PAR Readings and Longevity

I first got interested in lighting when I setup my 180 gallon tank. At that time I was running VHO lighting, and I knew I wanted and needed better lighting for the type of reef tank I wanted to keep. At that time, late 2004, I did a bunch of research at Reef Central. I met a guy from Montana, who went by the name Grim Reefer, he was experimenting with a lighting system that was popular in Europe but was pretty new to the United States, T5. After a bunch of conversations with Grim I decided to go with T5 lighting for my new tank. You can find more about my lighting system on my equipment page.

I've been looking to do readings with a PAR meter, and I convinced my local reef club, WAMAS to purchase one. Once I got my hands on it I did some tests on my tank. This was back in September of 2005. At that time my tank had been setup with the T5 lighting since February of 2005. I took these readings as pretty good as they compared favorably with other readings from the club of 250W MH bulbs (readings taken right under the bulb). You can see the results from my measurements in the table on the right.

I figured I was going to change out my bulbs at approximately 1 year of use, and sure enough in early March I got the PAR meter back, and took it along with a new set of bulbs and set to work doing the replacement. I did a second set of measurements and compared the results to the first. Interestingly enough the PAR measurements were very close which didn't really surprise me. I did think that the bulbs probably decreased a small amount ~10% based on the comparision of the surface readings, but I had started running ozone and felt that cleared up my water causing the deeper readings to be closer to the original even though the surface reading was less.

A couple of notes on the readings in March as compared to September:

1. The surface reading is ~1" "above the water surface (I'm keeping consistant with what our club is doing)
2. The bulbs configuration is slightly different from the readings in septemeber to march (I replaced one of the T5 actinic bulbs with a URI VHO actinic)
3. I've been running ozone since december which visually makes my water clearer (at least to me)

At that point I replaced the bulbs and got the shock that I wasn't expecting. My PAR increased dramatically. Again see the chart on the right. The only major difference was that I now was using GE 6500K bulbs as compared to the ATI 6000K bulbs. I will continue as much as possible to document weekly the change in PAR to see how these bulbs decay. For completeness I did PAR tests on all the bulbs I have in my system as well as 3 of my older bulbs for comparision. Sell the table on the left. I will also try to track these as well.

So stay tuned for more information. Ohhhh for you techies I did use an apogee meter for the testing. It's mounted to a piece of 1" PVC. I have a PVC T glued to a magnet for cleaning the tank and I use that to make sure I'm getting stable readings. Any questions feel free to contact me.

I wanted to add an additional update on this page, due to a setback with some of my corals I've changed my lighting around so the measurements are not as relevant any more. I can still post some PAR readings, but the bulb setup has been changed (I belive I was actually scorching some of my corals).

DHOCH