Influence of sand bed to PAR distribution

[meermann]

Hi guys,
does a tank with white sandbed really have better PAR distribution inside in comparison with the same tank, but with bare bottom and let say black cabinet top?
I noticed that lower parts of acroporas branches aren't colored as good as upper and have significantly less polyps number there.
Will reflection of light on white sandbed improve the health/coloration of lower branches or we shouldn't consider is as a meaningful factor?

What do you think?

 

[Ron Reefman]

Hi guys,
does a tank with white sandbed really have better PAR distribution inside in comparison with the same tank, but with bare bottom and let say black cabinet top?
I noticed that lower parts of acroporas branches aren't colored as good as upper and have significantly less polyps number there.
Will reflection of light on white sandbed improve the health/coloration of lower branches or we shouldn't consider is as a meaningful factor?

What do you think?

These are my opinions based on 20 years in the hobby and having used all 3 light sources (MH, t5 and leds).

What kind of light fixture are you using? MH, t5, led, hybrid?

IMHO, light reflected off the sand is of almost no value. Sand doesn't really reflect light well enough to make much if any difference. t5 and MH may reflect some off the vertical glass and do better than most led fixtures that are more directed in a vertical path by lenses.

Lower branches of most any coral will not do well after the direct light is blocked or reduced by the upper levels of the coral. MH and t5 probably have less issue here than leds. And single source (i.e. led pucks) have an even bigger problem than led fixtures with a wide array of leds.

 

[meermann]

What kind of light fixture are you using? MH, t5, led, hybrid?

Hybrid AI Hydra 32HD + AquaticLife T5HO.

The question was initially raised after discussion about disadvantages of black sand. It was stated that white sand is preferable because it reflect light and increases PAR on the lower parts of SPS.

At the moment I have bare bottom and considering to add a kind of sand bed if it improve the light distribution.

Discoloured lower parts of SPS don't bother me at all, but if something could be improved easily, why not.

 

[Ron Reefman]

Since you have a bare bottom tank, how about a mirror under the tank? A crazy idea for sure, but then I love crazy ideas. How many reefers have white tanks?

 

[garbled]

I know alot of people who do barebottom use a black ABS sheet on the bottom for protection against rocks. They also sell them in white... I'm actually planning to use white on a pico build I'm doing.

I doubt it contributes 100's of PAR to the underlighting, but I cannot imagine a black bottom is the same as a white/sand bottom. I mean, shine a flashlight at something white and black and look at the difference in the room behind you. There is definitely reflection. Even white carpet reflects light.

 

[NeonRabbit221B]

Lighting is interesting. Reflectance shouldn't be a major factor is white sandbeds but honestly don't know if there has been any studies out there. A mirrored bottom would be interesting but fish may ram against it trying to get to the other fish.

 

[meermann]

Since you have a bare bottom tank, how about a mirror under the tank? A crazy idea for sure, but then I love crazy ideas.

I thought about white styrofoam under the tank (reflection > 85%, not too much difference with mirror), but there are coraline algae spots and I need to clean it somehow often. Also I think some fishes could try to fight against their reflections (like zebrasomas do) - not so good.

 

[meermann]

I doubt it contributes 100's of PAR to the underlighting, but I cannot imagine a black bottom is the same as a white/sand bottom.

The problem of bare bottom/ABS it's quickly covered by coraline algae spots and becomes rose/violet instead of white. With sand bed made of white sand I could manage cleanness with let's say CUC like sand shifter gobies etc.