I am curious to see who uses T5 lighting. I have read that they don't need to be replaced until after a couple of years. I been using T5 for 6 months now and would like to know when I should think about replacing. My VHO's were every 6 months.
I have also read that after 2 years the output is reduced by 20% so I guess if the system can be sustained at 80% output there should be no problem. Given that information I will be replacing mine. My system is already lower light than I would like to have.
I've been using T5 lighting for a few years now. Good bulbs will definitely last two years. It's probably a good idea to replace them after two years though. They do lose a little bit of punch, but not much.
I dunno - I have been using T5HO for a couple of years now in 3 different fixtures, 1 Catalina and 2 Tek lights. I also know a number of folks in our local group that run Tek lights and I will say that typically after about 9 months T5HO's are SIGNIFICANTLY dimmer than new bulbs. As such, I typically replace mine every 9 months, as do other folks that I know.
I do not believe it has anything to do with the bulbs. I have been through Giesemann, Aqua Medic, CoralVue, UV Lighting, etc all with similar results.
I cannot say that the bulbs are NO GOOD after 9 months, but they definitely give off significantly less visible light - very easy to see the difference if you plug a new bulb in next to the older ones and light them up.
I have heard that it is T5NO's that can last you up to 24 months - perhaps because they are not being overdriven...
I've used coralife T5 (the cheap ones) for two years and the output is very noticably diminished after only about eight to ten months... I know this because I've got two two-bulb fixtures and I've changed them two at a time since I got them. I'd say they diminish at nearly the same rate as the regular T12 or T8 bulbs, and should be changed every year or so.
Rule of thumb is;
T12 and T10 every six months. I have a chart some where that shows the decline of the cathode tube.
T8 every year
T5 (including CFs/PCs) annually
T5HO dunno yet.
T12 actually can decline 60% in six to 12 months. Other more efficient tubes can go longer but the cathode tubes all decay over time. I'd never wait until they burn out. The intensity deminishes too much and the spectrum (spectral outout)can be altered. The Triton tube (a T10) by Interpet claimed that this bulb would not change in intensity or spectral output from day one until it burned out. Not sure how they are the only ones on the planet that can accomplish this.
I have Hagen T5HO bulbs that are around 8 months old so I've ordered some Giesemann Middays to replace them. Of course this isn't an apples to apples comparison as to whether there's any visible difference in intensity of new bulbs vs old. On a side note, I also have an Aquaflora on the way since my curiosity about those got the best of me.
The Giesemann's arrived today. I bought two Middays and one Aquaflora. I ordered them from Aquarium Specialty in Columbia SC. Pricing was $19.00 for the Middays and $20.50 for the Aquaflora 48 inch bulbs. Customer service was great. I placed the order on Sunday and received an email on Tuesday that the Aquaflora bulbs were on order and should arrive on Wednesday and my order would be shipped after that. It shipped on Thursday and arrived today.
On to the bulbs. I've been running one Hagen LifeGlo with a PowerGlo for 10 hours a day and a two hour noon burst with two LifeGlo's for a couple of hours. I tried both Middays together and a Midday/Aquaflora combo. The appearance of both Middays was a bit yellower than what I've been running but it was a natural warm appearance and the reds in my L cuba and P stellata were still prominent. The combo looked a bit less yellow and the reds may have been a little more pronounced but the appearance was close enough for me not to be a big deal either way.
One of the more noticeable things to me was the increase in pearling almost as soon as I flipped on the new bulbs. So I guess my old bulbs were ready to be replaced.
I do like them. They don't have that really green look that running two of the 6700k LifeGlo's has ( which is why I was using a PowerGlo/LifeGlo combo ). It's a warm natural look, as I said above, that I really like. They're a keeper and I'm looking forward to seeing what the plants think of them.
Perhaps all of our old references about the effective life of aquarium lighting are more hear-say than fact? If I understand you right, T5 bulbs do NOT have an effective life of 18-24 months, yet this is the "common knowledge".
This would confirm my experience as well as the experience of a number of local hobbyist in AZ...