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  • Ageing T8's

    Hi,

    I have some T8 tubes over my tank. As they age, my understanding is that the light output from them starts to drop off. Does the spectrum of the light also start to change slightly too?

    From what I think I read a while back, plants don't really care too much about the spectrum (despite what product marketers tell us). Is that correct?

    And, as the lights age and the light weakens, wouldn't this be a good thing down to a point (lower CO2 requirements etc).

    How can I really tell when old enough is old enough?

    Scott.
    6' Planted Tank (72" x 18" x 20") - 4 x 30W T8 Tri-Phosphors - 2 x Eheim 2217 'Classic' canisters
    Flourite substrate - Ocean Runner OR-2500 + AM1000 - Tunze Turbelle Nanostream 6045
    6.8kg Catalina CO2 - Red Sea Pro regulator - Swagelok B-SS4-A metering valve - Vecton 600 UV

  • #2
    There was a really good thread on here a while back about how the drop off in intensity for flourescents isn't nearly as bad as initially thought. I can't locate it at the moment but I seem to recall the replacement suggestions typically bandied about were not necessary after comparing new/old bulb PAR values. Spectrum shift for flourescents is probably not a big deal and I would be surprised if there were a large shift in the Normal Output lamps. I could see some of the HO or VHO might shift but any shift or lack thereof is mere speculation on my part.

    Hopefully someone can find that thread and chime in here.

    -
    S

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    • #3
      The spectrum also start to change, I have 2 blue tubes that with time they get whiter. Plants care about spectrum, not is the same growing un blue lights only or red lights. But in general they love more intensity than spectrum preferences. You need to change the tubes before the light output start to drop a lot and the spectrum changes a lot. Everybody says 6 months for T12,T8, spiral fluorecents and pl. I use good ventilation and my T12 not gets hot, they still works 8-9 months but the light output is dropping. The best is to change it every 6 months, they seems like new and maybe the intensity only drop a little but you dont want a 1600 lumens ouput to drop to 800 lumens. Some people uses the tubes for 12 months, if you have easy plants is ok, but red or hard plants feels that and can die or turn green. Also the quality of the tubes can make great changes in intensity and lifespan.

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      • #4
        Originally posted by shoggoth43 View Post
        There was a really good thread on here a while back about how the drop off in intensity for flourescents isn't nearly as bad as initially thought. I can't locate it at the moment but I seem to recall the replacement suggestions typically bandied about were not necessary after comparing new/old bulb PAR values. Spectrum shift for flourescents is probably not a big deal and I would be surprised if there were a large shift in the Normal Output lamps. I could see some of the HO or VHO might shift but any shift or lack thereof is mere speculation on my part.

        Hopefully someone can find that thread and chime in here.

        -
        S
        This one?
        http://www.barrreport.com/showthread...n-PC-Bulb-Life
        It's mainly for PC bulb though. But newer T8s such as Philips 865 claims to retain
        90% lumen for 20,000 hours. (Panasonic bulbs claim longer than that but I don't like the color)
        http://www.lampspecs.co.uk/Light-Bul...ylight-Philips

        Comment


        • #5
          I tested some PAR data for CSL 8800K bulbs that where 3 years old compared to the new ones.
          Maybe 5% drop over this time frame.

          Regards,
          Tom Barr
          www.BarrReport.com

          Comment


          • #6
            WOW, that means NO T8 have a bigger lifespan that T5 HO???

            I dont like the first drop in PAR, that is amazing fast.

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            • #7
              As the thread says, ballasts make a giant difference. That's the lifespan with an electronic ballast; there's still plenty of magnetic ballasts hanging around. T8's that come stock with hoods are usually magnetic; far shorter lifespans on them, and their intensity seems to dim faster.

              That's just subjective though, I haven't done the PAR meter work.
              - Dan

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              • #8
                In my case I use Electronic ballast, I know there are better ballast than other, the price changes a lot.

                Comment


                • #9
                  It also depends on the cost of the T8 bulbs, if they are cheap and you can get them somewhat easily or in bulk, then once every 2-3 years is fine with an E ballast.
                  PAR does not change much, color does, more aesthetics for myself.


                  Regards,
                  Tom Barr
                  www.BarrReport.com

                  Comment


                  • #10
                    The T8's that I use are 'proper' aquarium NEC tri-phosphors (30W). I have no idea what sort of ballast I have - I am using 6' light fitting with external ballast designed for aquarium use (by a company called Dalbarb).

                    I have been using the same tubes for 6 months, I suppose I can just go on using them until despite all efforts the plants start to really slow down?

                    Scott.
                    6' Planted Tank (72" x 18" x 20") - 4 x 30W T8 Tri-Phosphors - 2 x Eheim 2217 'Classic' canisters
                    Flourite substrate - Ocean Runner OR-2500 + AM1000 - Tunze Turbelle Nanostream 6045
                    6.8kg Catalina CO2 - Red Sea Pro regulator - Swagelok B-SS4-A metering valve - Vecton 600 UV

                    Comment


                    • #11
                      Originally posted by scottward View Post
                      The T8's that I use are 'proper' aquarium NEC tri-phosphors (30W).
                      From this chart: http://www.hereinspaziert.de/Lampen/Bild2.htm (from paludarium's reply in this thread
                      http://www.barrreport.com/showthread...n-PC-Bulb-Life )
                      Then it probably lasts as long, since Dreibanden (German) means tri, so I suppose it's tri-phospher.


                      Originally posted by scottward View Post
                      I have no idea what sort of ballast I have - I am using 6' light fitting with external ballast designed for aquarium use (by a company called Dalbarb).

                      I have been using the same tubes for 6 months, I suppose I can just go on using them until despite all efforts the plants start to really slow down?

                      Scott.
                      If your bulbs turn-on immediately without flickering first.
                      Then your ballasts are electronic.

                      Comment


                      • #12
                        I don't post so much in aquarist forums these days but this one got me. lol

                        Forget the 6 month rule even on magnetic.

                        The chart above is a good one. It shows that when the tube is 'burning in' there is a large drop in PAR and then it straightlines for the next 2 years or so.

                        As someone above stated, in general stock T8s will have magnetic ballast BUT not quite so likely on newer setups. Older (and budget) ones will almost definately be magnetic.

                        On the electronic ballast part, yes electronic ballasts will make tubes last longer BUT instant start electronic ballasts will not be a huge amount better than magnetic in longevity although they will keep a more constant intensity. programmed or delayed start electronic ballasts are the ones that increase the tube lifetime. Not sure on the technicalities but I think they hold the power back until it reaches and ideal then starts the tube at the ideal rather than building like the instant start ones.

                        The white paper hasn't changed BUT the page I linked to ages ago has been altered so it isn't as easy reading. basically they measured Lumens (not our baby I know) and they held 95% of initial lumens over 40% of the tube life which at a conservative assumption of a tube being 20000 hours made 40% 8000 hours. That means 1000 days x 8 hours which is nearly 3 years. That is conservative!!! I would expect PAR to be reasonably close in dropping off as the Lumens are or at least within a reasonable difference as the Lumens may drop as the tube gets older due to spectral changes whereas the PAR will not.

                        T5HO versus T5/T8 is one of my favourite arguments. Both T5 and T8 provide more light per watt than T5HO, however T5HO provide more light per inch. This means if you have 1 T5 or T8 tube that is 3ft approx then it will not give as much light as a 3ft T5HO, however there will be more light per watt. This means that 2 x 3ft T8/T5 will provide more light than 1 x T5HO even if the 2 tubes add up to the same wattage as the T5HO.

                        The point I make is that for our purpose where we aren't after huge swathes of light then we can afford to use 2 or 4 T5/T8 tubes rather than use 2 x T5HO to get the same wattage but less total light. For reefers who do want the mass light then being able to pack more light in a smaller space is great. for us to be able to use more tubes without getting too high on light means we can spread the light out and achieve almost perfect results That is in my eyes the success of LED. The ability to spread the light out and not create 'hotspots' and 'blackspots'.

                        As for the 'real aquarium tube' argument. If you want to pay the money do so, but don't assume that because it says 'aquarium plant grow' that it will be better than any other tube of the same K etc. Price does not necessarily dictate the quality nor does the ink use to print 'aquarium' on the tube. A good brand standard tube (Philips etc) will more than likely beat most of the aquarium tubes on the market (likel for like in K etc) but because it doesn't have 'Aquarium' printed on it then the Philips will be half the price or less!!!

                        AC
                        www.greenneedle.co.uk

                        Comment


                        • #13
                          I have 6 T12 tubes in my aquarium, they have 8 months, still I dont see a lot of drop in intensity, still they looks good, 2 of the 6 are for aquarium :

                          http://www.fosterandsmithaquatics.co...tid=3810&rel=1

                          2 are phillips daylight (6,500 and 5,500) and 2 are GE for plants and aquarium (really cheap $6 a tube). Im thinking to change to T8 but I dont know if buy Hagen T8 tubes because seems great the specs, or go with cheap phillips tubes???

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                          • #14
                            Waiting for answer please.

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                            • #15
                              go with the philips
                              www.greenneedle.co.uk

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