t8-t6's

[AdAndrews]

Does changing the bulbs over from a t8 unit to t6's have any actual effect to plants, apaprently, t6's are 40% brighter, but i have just read that as the surface area of the t6 is smaller than t8, the light is simply more concentrated when looking at it, however, because no more watts are being added, the light is the same as before :?:

thanks,
Adam

 

[ceg4048]

Well, brighter means brighter. The same argument is made of T5's which also have a lower surface area than T8, but which we know from PAR measurements deliver more radiation. None of these popular parameters matter in a direct sense, not the surface area, not the wattage. The only thing that matters is the number of photos emitted and the number of photons which arrive at a certain distance from the bulb.

Having said that, both the shape and the size of the bulb will have an effect on the photon distribution, but ultimately, the most important item is the measured photon flux density at distance. Unless you can measure PAR at reference distances it's not possible to determine the change in effect from one bulb type to another.

Cheers,

 

[Nick16]

^^^ im going to have to translate that!!

with T6's you would expect more light to be piercing further down the water coloumn as opposed to the T8's.

 

[ceg4048]

And that can only happen if the light is brighter. Again, this is another misconceived parameter "water penetration". The only reason a given light penetrates freshwater deeper than some other light is because it's brighter. Not because of any voodoo or special quality of the bulb technology.

In natural salt water systems the story is radically different. Lower frequencies, such as red, yellow and green get absorbed at shallower depths, so that only the highest frequency light can penetrate to the lower depths. This means blue and indigo are the last to be absorbed, and that's why the ocean appears blue. In a marine tank though, you'd need at least a 15 foot depth before you'll start to see falloff of the lowest energy (Red). Again, this assumes that the light source mimics the sun's spectral energy profile. Since no bulb can even dream of mimicking the sun's profile the penetration issues are more complicated due simply to missing or subdued frequencies.

By about 50 feet every color produced by the sun except blue is absorbed. By about 330 feet the last of the sun's blue is absorbed by the ocean.

In fresh water (as well as in salt water) there are other factors, such as angle of the sun, latitude, refraction, reflection, planktonic activity and turbidity that limit light penetration in natural systems. In our case, at our very shallow depths, the only factor limiting PAR penetration is strictly the bulb output. Either it's bright or it's dim, and the brighter it is the deeper it penetrates.

Therefore, if the T6 bulb appears brighter to you then that brightness will translate to a deeper penetration towards the substrate.

Cheers,

 

[AdAndrews]

Awesome guys. That explains alot, Clive.

thanks for your help.