How high to hang the light above the aquarium?

[Bradders]

Hi All,

Struggling a little with this one.

If you hang your light (in my case, the WRGBII Pro90cm), how do you calculate the right distance?

Maybe it does not matter, but can seem to find this information anywhere .......

Brad

 

[Connswater]

Hi All,

Struggling a little with this one.

If you hang your light (in my case, the WRGBII Pro90cm), how do you calculate the right distance?

Maybe it does not matter, but can seem to find this information anywhere .......

Brad

Great question, ADA/Chihiros/Kessel would you think have recommendations, but I haven't seen them. I tend to go with around 8-12 inches, but with a really intense light I suspect 18 inches above the top foliage would be about right, but a pure guess on my behalf. I tried 18 inches with 30 and 50 watt LED floods but that was too high, dropped down to around 8 inches and there was a noticeable improvement in growth and pearling. I will be intrigued to find out what folks know/think.

 

[MoFish]

I would have thought you just set it at a sensiible height which also looked good to you, then adjust the power via the app to optimise it. I assume it matters more what hieight you set it at when you have single light source (e.g. ADA Solar RGB or Chihiros Vivid), because then you have to take into account how much the light spread such that there is no dark corners.

 

[Bradders]

I would have thought you just set it at a sensiible height which also looked good to you, then adjust the power via the app to optimise it. I assume it matters more what hieight you set it at when you have single light source (e.g. ADA Solar RGB or Chihiros Vivid), because then you have to take into account how much the light spread such that there is no dark corners.

Yeah, the WRGB Pro II is a single light, but with lots of LEDs. I think my question is about the effective angle of the light where its not too high or not too low.

 

[MoFish]

Bit unclear from me sorry. By single light I meant lights which are significantlly smaller in terms of length comapared to your aquarium length (like a spotlight, but not sure if solar rgb/vivid fall into that category). I assume you're using the 90cm light on an aquarium which is 90-100cm? in which case the angle probably doesnt matter that much and you can set the light to whatever height looks good to you, within reason.

 

[Nuno da Silva]

Maybe it does not matter, but can seem to find this information anywhere .......

I think you're right here! It doesn't really matter, as long as you're aware that the further away from the surface, the less light will be reaching the bottom of your tank. Your light is actually controllable so you can set it really close and adjust the intensity. Without controllable intensity, you could use the hight to achieve the same effect.

 

[Maf 2500]

It will depend to a large extent on the beam angle of the LED's in the light, or any lenses. The height of the legs for mounting on the rim of a tank will also indicate the sort of height that the manufacturer designed it for. Hang it much higher than this and you are going to get lots of light spilling out the sides before it even hits the surface.

They also sell reflective side shades for the WRGB II Pro which would allow you to hang it higher without losing so much light out the sides.

​

 

[oreo57]

Hi All,

Struggling a little with this one.

If you hang your light (in my case, the WRGBII Pro90cm), how do you calculate the right distance?

Maybe it does not matter, but can seem to find this information anywhere .......

Brad

Well it actually matters a lot for light spill and light "entrapment" into your tank.

With dimming it diminishes the need but not if one cares about optimization of your $'s.. 😉

Start with the simple geometry involved.

LED Lighting Beam Angle Calculator

A simple calculator that determines spot size by a light's beam angle

store.marinebeam.com

Ideally you want a height that captures as much of the output into the tank as you can reasonably get.
Once light enters "in the tank" glass reflection and water refraction contains a lot of the photons.

Take a simple example of a single row of leds. most "stock" emitters are lensed around 120 degrees.
At 120 degrees and 6" off the surface of the water the led spreads its photons over a circular (roughly) area of 20.78" (52.8cm)
Say you have a tank that's 18" (45.7cm) wide. "Ideal" height to keep all the photons inside the tank proper (at the water line) would be around 5.2" (13.2cm)

If you hung the light at say 30.5cm (12") your spread would be 105.66 cm (41.6") with a 120 degree lens.
with a 45cm wide tank most of your light will not be in the tank but in the room.

Obviously with multiple row lights and the FWHM concept it gets a bit trickier.

Easiest thing is to take a large white sheet wit the dimensions (surface area) of your tank and raise or lower your light until you visually see that most of the light is inside that boundary.

A fun primer from the saltwater world..
EDIT.. I replaced the vid with a link that starts at the AquaMaxx tests since they are more "freshwater design" like than most of other light.
Many saltwater lights are 90 degree lensed or narrower.

 

[Bradders]

Thanks @oreo57. That is a great explanation.

I think I can work with that and get a reasonable level of correct height.