David C

There is much confusion concerning T5 bulbs compared to T8 bulbs and because of my OCD (actual diagnosed) I spent quite a bit of time trying to figure out what lighting I wanted for my new tank. Along the way I have had an electrician friend of mine help me out switching out lighting fixture hardware and using a meter to determine light effectiveness. My methods may not be exactly scientific, but they were the best I could manage short of calling MythBusters. Using the same fixture and reflector, I put in a new T5HO 6700k bulb and tested the amount of light at the surface, half way down in the tank, and the bottom. Then we switched out the hardware for T8NO 6700k bulbs giving off almost the exact same wattage and redid the testing. The single T5HO bulb and the two T8NO bulbs giving off nearly the same wattage produced very similar results, but the T8 bulbs took up much more space in the hood.

I've spoken to rep's at both a fixture manufacturer and a bulb manufacturer to confirm my own testing. Under the same conditions, T5 bulbs smaller diameter allows more bulbs in the same hood space, more bulbs equals more potential light. High Output (HO) bulbs allow higher wattage per bulb, so more bulbs fitting in a fixture X higher wattage per bulb = more potential light. 160watts of T8NO light under an equivalent quality reflector and ballast will produce almost exactly the same light in a tank as 160watts of T5HO light. There will be a slight difference in amounts of light, but not a drastic difference. Most differences noticed when upgrading lighting fixtures is the quality of the reflector and ballast is far superior to that of the stock fixtures.

This comes from my own testing and confirmed through the companies that manufacture the products. What you get when you purchase the expensive fixtures is quality designed reflectors and ballasts. I'm no electrical genius and I'm sure there will be a ton of people who say I'm wrong, but it is what it is.

Dave

Regal

This is interesting. You should post some Mythbusterish pics if you have them.

I'm confused though. You said you tested one t5HO bulb and two t8NO bulbs and they both gave you the same amount of light but then you said that 160 watts t5HO is the same as 160 watts t8NO. I'm sorry if I'm reading something wrong. What is the wattage on the 6700k bulbs?

I have found t5HO to be really bright. On my 75 gallon I have 260 watts in a Power Compact fixture and on 55 gallon tanks I have 108 watts T5HO. Both tanks are 4 feet wide. When I look at them both the t5s seem brighter than the PC light with more than twice the watts. I don't have a light gage though. I'm just eyeballing - which is not very Mythbuster

Is your reflector white?

David C

I used the silverish reflector that comes standard in my T5HO fixtures. I used a single T5HO bulb with a rating of 54watts and a pair of T8NO bulbs with a combined output of 60watts. Using the meter, the T8 bulbs came out slightly higher, but proportionally it was lower because of the slightly higher wattage. According to the fixture manufacturer I spoke to, the difference in the visible light between your stock system and your upgraded Power Compact fixture is the new one comes with a higher quality reflector concentrating more of the light towards the aquarium, also you probably made a pretty big change in wattage making the bulbs look MUCH brighter as well.