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Do t8 lights really degrade over time?

terry82517

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18 Jan 2013
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Hi all, I have 2x 30 watt t8 bulbs in my rio 180, co2, ei dosed planted tank, have had the bulbs for longer then I can remember and I'm thinking of replacing them as I've read that they lose their power after a year or so. Is this true or some another ploy to get you to buy new bulbs all the time?
 
You will hear different opinions about this, personally I think they do produce less light over time & change mine as a matter of course every year.
If your plants are growing well then the only reason to buy new would be for a fresh colour but, if you do I would only change one at a time just in case they are much brighter, you dont want to encourage algae growth with to much light!
 
Is this true or some another ploy to get you to buy new bulbs all the time?
Yes it's another ploy. It doesn't matter one iota if the bulbs lose some of their PAR output. The plants will adapt and increase their absorption efficiency. And people use way too much PAR to begin with, so it's actually a good thing if the bulbs drop their output.

Cheers,
 
It depends whether your tank is set up to rely on higher lighting levels too. I cannot believe that if a tank is running well on a certain level of light, and that light level degrades over time, that you will achieve the same results. I see what CEG means about the plants adapting, but surely that means they would grow slower ? That would not bother many people mind you. (Though I am quite pleased how quick my Pogostemon and Rotala is growing at the moment as I cant afford to buy extra plants to fill out the gaps they are filling hehe).
 
Depends on what you imply by 'the same results'?
We all know that C02 is the governing factor & light is used to match the gas supply, so if the light lessens over time & the gas remains at the same level the most likely even will be an overall cleaner tank.
I mean the plants will be healthy & the chance of algae decreased, probably resulting in not even a hint of algae, so yes there will be different results but necessary for the worst!
If you mean plant growth will be slower with less light then possibly yes but not necessarily by much!
 
Depends on what you imply by 'the same results'?
We all know that C02 is the governing factor & light is used to match the gas supply, so if the light lessens over time & the gas remains at the same level the most likely even will be an overall cleaner tank.
I mean the plants will be healthy & the chance of algae decreased, probably resulting in not even a hint of algae, so yes there will be different results but necessary for the worst!
If you mean plant growth will be slower with less light then possibly yes but not necessarily by much!


Hi foxfish, yes i was referring to plant growth rate primarily. You say not necessarily by much. Are there any studies that can give actual figures on this ? Its an interesting topic. For example, if say my lighting levels were reduced by 50% output due to tube degradation would that be reflected by a 50% reduction in growth rate ? If so, I can imagine some people not being prepared to wear that (especially when many want their scapes to grow in relatively quicky for competition images). But if it would only be reflected by say a 5% reduction then it would not matter as much.
 
Hi,
First of all it's not really a good idea to rely on higher lighting levels because light only has a positive effect on growth rate, not on plant health. In fact, just the opposite. Those who rely on high lighting almost invariably suffer plant health related issues. In any case, you will not be able to detect the reduction of growth rate because it isn't significant. There is a much higher affect on growth simply due to CO2 tweaking or due to nutrient concentration levels. You said it yourself. If you are satisfied with the growth rates why spend more money to get new bulbs?

Have a look at a thread regarding old bulbs. The thread discusses T5, but exactly the same applies to T8. Two new tubes... | UK Aquatic Plant Society

Cheers,
 
Hi Terry,
one thing to consider is that if you introduce new bulb/bulbs, you may need to increase carbon availability slightly again to compensate for increased par. The plants will have got 'hooked' on the current co2 and when trying to increase growth rates due to the increase in lighting imtensity could lead to issues. If the co2 is maxed regards fauna, liquid carbon is a good booster.
Alternatively you could decommission any reflectors if used or add extra floating plant cover. As Foxfish said, it may be a good idea to add one bulb at a time to reduce any ill effects.
Cheerio,
Ady
 
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Hi,
First of all it's not really a good idea to rely on higher lighting levels because light only has a positive effect growth rate, not on plant health. In fact, just the opposite. Those who rely on high lighting almost invariably suffer plant health related issues. In any case, you will not be able to detect the reduction of growth rate because it isn't significant. There is a much higher affect on growth simply due to CO2 tweaking or due to nutrient concentration levels. You said it yourself. If you are satisfied with the growth rates why spend more money to get new bulbs?

Have a look at a thread regarding old bulbs. The thread discusses T5, but exactly the same applies to T8. Two new tubes... | UK Aquatic Plant Society

Cheers,


Hi ceg, so you are basically saying that a large reduction in lighting output only results in an insignificant reduction in growth rate ? Im trying ot get my head around this as so many people seem to want higher and higher light levels. George Farmer has just set up a small tank with two whopping great TMC led's above it. I know that he can adjust the output of them as well as the height if they were not adjustable but it begs the question "whats the point". Are we getting conned by all the LED manufacturers, only in a different way to the flouro tube manufacturers telling us to replace our tubes every 6 months ?
 
Hi ceg, so you are basically saying that a large reduction in lighting output only results in an insignificant reduction in growth rate ? Im trying ot get my head around this as so many people seem to want higher and higher light levels. George Farmer has just set up a small tank with two whopping great TMC led's above it. I know that he can adjust the output of them as well as the height if they were not adjustable but it begs the question "whats the point". Are we getting conned by all the LED manufacturers, only in a different way to the flouro tube manufacturers telling us to replace our tubes every 6 months ?
For many I believe the led route is a lot to do with aesthetics and minimisation, plus as you suggest you have the control element which is great for a more natural light build up and reduction to assimilate nature. With this you also have a greater level of control over co2 introduction.
 
LEDs also have a lot to do with the whole hobby scene, folk like to be involved with their tanks & equipment & spend money on the latest kit - nothing wrong with that in my mind :)
It is a bit like the original question....it might or might not be necessary to change the bulbs but, I change mine every year because I want to!
There is more than one way to skin a cat, you can use hight light to grow plants fast, take a look at some of the American forums, those guys are crazy for light but you can also grow plants with low light & that seems to be the more effective overall method at this present time!
It is difficult to predict the future & perhaps views & techniques will change before long, however I am personally having great success with a short lighting period & less than 2 watts per gallon.
The thing is..... I kind of miss my mega watts tanks, I want to go fast on my motobike, I want to run faster than I ever have & I want mega watts on my tank LOL
 
For many I believe the led route is a lot to do with aesthetics and minimisation, plus as you suggest you have the control element which is great for a more natural light build up and reduction to assimilate nature. With this you also have a greater level of control over co2 introduction.

I think you are probably right. Best of both worlds then :)
 
Found this graph after a bit of a google - you can see that T8s never lose more than about 10% of their output, and that's after about 3 years of use (assuming 3500 hours a year if used for 10 hours/day in an aquarium). So I really wouldn't worry about changing them.

T5 and T5HO lose even less (about 5% of their output over their lifetime).

Halides do decay somewhat more significantly, but Clive's arguments still apply.

lightdecay.jpg


picture3ij.jpg
 
My lights came with the tank when I brought it second hand so god knows how old they are, have nothing to compare growth to as they are all iv had!

But the general consensus is only bother replace when bulbs stop working or blow I guess?
 
Yes...but can you grow carpet plants like glosso with decaying T8s?

Lets face it to provide the optimum growth conditions for high light plants you need quality over quantity. In other words high light in combo with optimized ferts, flow, and CO2...oh and timing...everything always comes down to timing, it's a rare universal constant.

The artistry is in getting the balance right, which isn't easy for the uninitiated - which I'm guessing is Clive's big frustration - lighting is not a panacea in itself.

George has two whopping great TMC led's because he understands this fundamental universal truth...he has more than an inkling how to balance stuff!
 
Yes...but can you grow carpet plants like glosso with decaying T8s?

Lets face it to provide the optimum growth conditions for high light plants you need quality over quantity. In other words high light in combo with optimized ferts, flow, and CO2...oh and timing...everything always comes down to timing, it's a rare universal constant.

The artistry is in getting the balance right, which isn't easy for the uninitiated - which I'm guessing is Clive's big frustration - lighting is not a panacea in itself.

George has two whopping great TMC led's because he understands this fundamental universal truth...he has more than an inkling how to balance stuff!

Confusing the point a little I think Troi - you'd stand pretty much the same chance using 5 year old T8s as you would brand new ones.
 
What? can you or can't you grow glosso under T8s?
I think like you, I'm not convinced you can (that is in the form of a dense carpet) and T8s do degrade quite markedly - IMO - over the period of a year or so; and that is kinda of the point in itself...but not all...

...all this talk about plants adapting to lighting conditions is all well and good but there still has to be an optimum for photosynthesis, especially for light demanding plants like glosso . And this may be controversial, but I think the spectrum has more to do with that than mere aesthetics.

But nevertheless, I think the point I'm trying to make is that light is just another nutrient and if other factors are not optimized - whopping great TMC's aside - Liebigs Law of the Minimum applies. Or am I still missing the point...I never know these days.
 
What? can you or can't you grow glosso under T8s?
I think like you, I'm not convinced you can (that is in the form of a dense carpet) and T8s do degrade quite markedly - IMO - over the period of a year or so; and that is kinda of the point in itself...but not all...

I have no idea, I've never tried. But the evidence is that T8s only degrade 5-10% over their lifetime, and I doubt that makes much difference one way or the other. If you've got evidence that they degrade more than that it'd be good to see, I'm just relying on a bit of googling.
 
I am pretty sure that George himself wrote about how he found the par rating diminished considerably over a quite sort time!
I might be wrong but I think there was even an article in PFC by George ?
Anyway if you are old enought to remember when every house was powered by fluorescent tubes - then you will remember that they do in fact lose brightness!
 
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