Old vs. New T5 Bulbs

[jcook54]

I've always read that you should slowly swap out old T5 bulbs for new ones. I'm running a 36" T5 hybrid over my frag tank. I just got in my new bulbs and since I have one of the Club's PAR meters I thought I would do a little bit of research. I picked a spot directly under the front 2 T5 bulbs and here's what I got.

All of the bulbs are 36" ATI Blue Plus and I only measured directly under the 'front' part of the hybrid fixture that contains 2 bulbs.

Old T5 bulbs - PAR of 155
One old and one new bulb - PAR of 165
Both new Bulbs - PAR of 190

So, if I were to swap out both bulbs at the same time my PAR would go from 155 to 190. Quite a bump! Instead, I put one new bulb in the front part of the fixture in one part of the fixture and one in the back. The other two will get swapped out in 2 weeks. All PAR readings were taken after the new bulbs had been on for an hour. Once I swap out the other two, I'm going to see how long it takes or them to "burn in" and come down to that 155 PAR. I know this isn't the most scientific results but it certainly shows why it's a good idea to not change out all of the bulbs at once. I used to have a straight 6 bulb T5 fixture an swapping them all out and once could have burnt some of the lower light corals I keep on that side of the tank.

 

[90gDreams]

How old is old? Curious how long it took to see a 20% drop in output.

 

[dball711]

I always replaced all 6 bulbs in my ATI fixture at the same time. Never had any adverse issues.

 

[timeconsumer]

Cool test. I'm curious if you know what kind of ballast your T5 fixture uses. Some fixtures (like mine) use a Fulham Workhorse ballast which is not specific to T5HO usage and does not have a program start, rather it has a rapid start function. I heard around the reefing community years back that a rapid start ballast will wear bulbs out faster than a program start ballast will.

 

[sharis100]

I typically swap my T5 bulbs out yearly all at the same time. In fact, just did the swap out on my tanks. Never noticed any ill effects. But good to know for future. Thanks

 

[ichthyoid]

Cool test. I'm curious if you know what kind of ballast your T5 fixture uses. Some fixtures (like mine) use a Fulham Workhorse ballast which is not specific to T5HO usage and does not have a program start, rather it has a rapid start function. I heard around the reefing community years back that a rapid start ballast will wear bulbs out faster than a program start ballast will.

The white paper below details this issue & effect on bulb life. The conclusions are at the bottom -

https://www.halcolighting.com/pdf/WP/Ballast-Start-Type-Lamp-Life-White-Paper.pdf

 

[timeconsumer]

The white paper below details this issue & effect on bulb life. The conclusions are at the bottom -

https://www.halcolighting.com/pdf/WP/Ballast-Start-Type-Lamp-Life-White-Paper.pdf

Interesting read but I wonder what their standard for lamp life is. When it loses 20% brightness or 30% or stops working entirely? I'm hoping to eventually find/gather some decent quantitative data on the subject though and understand what the PAR loss after 1 year is between the two different systems. I figured jcook's observations here are as good a place as any to start.

 

[ichthyoid]

It’s not just PAR loss, as there is also a spectrum shift with greater loss at shorter (higher energy) wavelengths.

 

[Adam]

That's exactly what I was going to say Bill. The spectrum shift is more important. That is when with older bulbs people start complaining about algae growth.

I'm still not sure I'd want to shock stuff with 20 to 40% more par all at one time in addition to a higher pur spectrum. Many have said they've done it with no issues but if all were swapped at once maybe cutting the hours back a little might be a good idea?

 

[jcook54]

The old bulbs were around 16 months old. I try to do it annually but I get busy. I feel pretty confident that I could have changed all 4 out at once without issue. Heck, I probably have in the past. When I was doing research on what bulbs to get (I always use the same one's but I still like to imagine a world where I was capable of making a change) I kept seeing recommendations to go slow or reduce the photoperiod with new bulbs. Since I have a handy-dandy PAR meter I thought I see what all the fuss was about. As far as ballast go - I don't know what kind they use in the Aquaticlife Hybrid fixtures.

 

[timeconsumer]

I'm pretty sure the Aquaticlife uses a spec T5HO ballast from HEP, very similar to the ATI ballasts. So in 16 months with a spec ballast and passive cooling you're measuring roughly a 20% PAR loss. Good to know.

 

[ichthyoid]

Best way I found was to write the date on bulbs using a fine tip Sharpie (maybe an ID code as well?). Then begin rotating them & keep track of days used.

When done right, the idea is to do staggered changes at regular intervals, with like amounts of days of run time on each bulb.