# T5 tube question



## Christos Ioannou (2 Jun 2015)

As far as T5 tubes are concerned, I can see that wattage reflects on the length of the tube:

24W @ 438mm
28W @ 590mm
35W @ 742mm
45W @ 895mm
54W @ 1074mm

Seems there is a _"naive correlation"_ between length and wattage (a factor of ~0,05)

Going to extremes, is it safe to assume that a 24W tube will deliver the same light (PAR)  as a 54W tube, at a perpendicular distance of 50 cm?


----------



## roadmaster (2 Jun 2015)

NO.
24 watts will not deliver same PAR as 54 watt bulb


----------



## daizeUK (2 Jun 2015)

I also assumed that a single T5 tube would give comparable lighting per unit area regardless of length.  If not then this would imply that shorter tanks with fluorescent lighting have lower light levels than longer tanks, all other factors being equal?


----------



## Rahms (3 Jun 2015)

Even individual tubes aren't equal along their length.  The first 10cm of a tube won't put out as much PAR as the middle 10cm. But it's not going to make a huge difference. I can't really see why it matters... No-ones going to buy a 1m bulb for a 0.4m tank, or two 60cm bulbs for a 1m tank, etc.

Think roadmaster may have missed that you're asking per unit area not a total measure, though. Wattage isn't a good indication of PAR.


----------



## daizeUK (3 Jun 2015)

To put the question another way, if you have a 60cm tank with a 24w tube and a 120cm tank with a 54w tube, both tanks being 50cm deep, and you measured PAR at a central point on the substrate in each tank would they be about the same?

I think that's what's being asked


----------



## Christos Ioannou (4 Jun 2015)

daizeUK said:


> To put the question another way, if you have a 60cm tank with a 24w tube and a 120cm tank with a 54w tube, both tanks being 50cm deep, and you measured PAR at a central point on the substrate in each tank would they be about the same?
> 
> I think that's what's being asked


Yes this is my question. If I want to copy a smaller successful tank (light-wise) does this statement make sense?


----------



## ceg4048 (4 Jun 2015)

Yes. More wattage is needed for more length of tube. PAR is comparable per unit length.

Cheers,


----------



## daizeUK (5 Jun 2015)

What about Juwel T5 tubes vs. standard T5 tube sizes?

e.g. a 24W Juwel tube is 18 inches whereas a standard 24W T5 bulb is 22 inches.

Does that mean that Juwel T5 tubes give more PAR because they pack the same wattage into a shorter length?


----------



## Christos Ioannou (5 Jun 2015)

daizeUK said:


> What about Juwel T5 tubes vs. standard T5 tube sizes?
> 
> e.g. a 24W Juwel tube is 18 inches whereas a standard 24W T5 bulb is 22 inches.
> 
> Does that mean that Juwel T5 tubes give more PAR because they pack the same wattage into a shorter length?



I suppose so, especially if they Juwel brand is labeled as HO. (High Output)
I think that the electronic ballast has some effect on the output of the tube as well.


----------

