Life of fluorescents

mrdemin

I recall someone saying they need to be changed every year or so... Is this because they stop working or because they just don't produce the same amount of light after long use?
I was having some difficulties growing baby tears, and just now thought "maybe its because one of my bulbs is over 3 years old!"
Thanks

aunt kymmie

The bulbs lose their intensity. Not enough for our naked eye to notice it, but the plants sure do. Sounds like it's time to change your bulb.

mrdemin

Wow that was QUICK! Thanks! I thought so too, but just wanted another opinion before I went to buy one. Good thing my second bulb is new!

Byron

You could be correct, three years is pushing a fluorescent tube. I would definitely replace it.

My fluorescent tubes still light when I replace them, which I tend to do every 12 months. It is a case of the intensity (lumens) diminishing as the tube burns.

The majority of opinion is that fluorescent tubes should be replaced every 12 months or sooner, though not all plant authorities hold this view. Kevin Osborne wrote a couple series of very good planted tank articles in the 1980's for FAMA and he advocated three years. Peter Hiscock recommends every year. And Karen Randall wrote of every six months being preferable but due to the cost every 12 months would work; she further suggests staggering the replacement (when there are 2 or more tubes over the tank) so they are both replaced after 12 months but at six month intervals to maintain a more consistent intensity long-term. Diana Walstad maintains that T12 tubes (the largest diameter) need replacement every year, but T8 tubes every three years. This thinking has support in a study by Wade Shimoda [using data from the Lighting Design Lab in Seattle] that I read on the krib showing that at 100% of rated lamp life a T8 tube is at 90% of the initial lumens while a T12 is at 75%.

While 90% may seem pretty good, also remember that the light actually reaching the plants is significantly less that what comes out of the tube, due to air, water, the cover glass, and the height of the tubes above the tank make quite an impact on light depreciation--another reason to have light fixtures right on the tank. So a weakening from the tube itself will be multiplied by other factors.

A local hobbyist told me of his experiments with a lux meter, and concluded that the depreciation after just three months was quite noticeable, and it went steadily down from there. I do know that when a tube is replaced after 12 months, the light in the aquarium is noticeably brighter under the new tube; so while I cannot see any weakening day to day, there certainly seems to be a gradual weakening in intensity.

Byron.

Angel079

I pers also change mine every 12-15 months, just keep the "old" ones for shop lights etc since they're still working.
Funny you say that about Baby tears, I tried it now for the 1st time in the 55g and was pretty certain they weren't gonna do cause its so "deep down" but I'm impressed how well they grow now. At first mine tried dieing off on me when I had them on the gravel somewhat 'planted' but then I took piece of screen, attached them to it and all this together to driftwood - Works wonderful since, looks kinda like a bunch lil stars lol (you can see a closer up shot on the "New 55g" pictures).

iamntbatman

I've also heard rumors around about color temperature changing as the bulb's life carries on, but considering the way fluorescent tubes work this is nonsense. We're talking line spectra here, not black body radiation. I think the problem with keeping tubes too long is purely due to actual light intensity output decreasing over time, likely due to the gases slowly leaking out of the tube.

mrdemin

Well I replaced the Eclipse Daylight with a Zoo Med 5500k (forget the name), I think the eclipse was also 5500k. It might be my imagination, or my eyes didnt adjust, but it seems brighter when I turned it on. The damn thing was 17 bucks, I should've went across the street to a hardware store, oh well.
My problem is that this Zoo Med, and the All Glass that I purchased a bit back both flicker before firing up... This is annoying to me, I can imagine its annoying to the fish as well especially when they turn on in the morning and its fairly dark in the room (Might have to start leaving my blinds more open).
Thats all for now, hope the plants start to grow quicker and I want to try adding baby tears again. I also started using Excel.

Byron

At 5500K the Zoo Med is probably the Tropic Sun, I had one last year on my 70g. Never had it flicker beyond a few seconds at start-up. Some tubes are worse at this. I have two All Glass fixtures, new last July, and they are instant start and the flicker is very momentary, scarcely noticeable. May be different tubes... who knows.

One suggestion, always have good light in the room when the tank lights come on and when they go out. My schedule now is to have the tank lights on at 9 am, and the blinds are open so the room is lit. In the evening during winter I have a wall fixture that is also on a timer and it comes on a few minutes before the tank lights go out, and remains on for half an hour. This settles the fish incredibly. The wall light didn't come on one evening when I happened to be watching the fish, and the tank light went out and several fish jumped and hit the cover glass, and I could see otherrs frantically swimming around the tank. When the wall light is on, this never happens, they all swim to towards the light but calmly.

Byron.