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
