Mirror
Darren, don't take this wrong but I think you need to reed the definitions of Specular reflectivity, and Diffuse reflectivity. from what you are posting it sounds like you think Diffuse reflectivity doesent reflect at all. this is just wrong.. actualy here is the definitions for all to see Oh there is also Spread reflectivity which is kinda a mixture of both..
"Specular reflectivity is the type that occurs in a mirror or any other highly polished surface. In the case of specular reflectivity, the angle of the reflection is equal to the angle of incidence. When we look into a mirror, the objects we see are at the same angle to the mirror as the angle at which we are looking at the mirror. Spread reflectivity is similar to specular reflectivity, but the reflected light is more scattered about the reflected angle. Diffuse reflectivity, as the name implies, is reflectivity where the reflected light is spread in all directions. An example of a diffuse reflector is a white painted reflector."
now havign said that... which one is better.. it totaly depends on what you are doing.. if you are rich and can afford lots of MH bulbs then go for the "Specular reflectivity" ie. spectral alumium (which is what I am using for my floresents) but if you can only aford say 1 MH for a 3 foot tank or 2 for a 5 foot tank you might be better going with a "Diffuse reflectivity" type reflector like hammer tone or good forbid white painted flashing. [img]images/smiles/icon_smile.gif[/img] the idea is to spread the light over more of the tankto get a even lighting and make due with what you have. I have seen tanks that are realy bright in one area and dim in another becuse they coulden't aford enuf lights and quite franky it looked bad IMHO.
I know you have enuf lights that you don't have to worry about this and by the sounds of it most estableished reef people on this board do also.. (Andrew when are you going to host a meating so we can get a chance to see your tank?) but for people who are putting togeather new systems and want to spend more money one substrates and skimmers and such, or are not planning on keeping SPS for a while a "Diffuse reflectivity" type reflector might be the best bet, keep in mind I do not avocate the painting of the inside of your hood to make a reflector becaus it is just plain flat and won't work as good as if you bent up a piece of white flashing.
to see what I mean take a small piece of "shiny white flasshing, and a miror. go to a dark room and shine a focused been of light into the miror so it reflects onto the wall.. then do the same with the flashing.. the circle from the flashing will be a lot bigger than the one made by the miror, yes it will be less intense but it will give a larger area the same amount of even light. enuf said about that.
Also I think victors idea of blowing the back (or side) of the reflector instead of the water surface would be good if you wanted to cut down on the evaporation rate.. the more air yyou have blowing at the surface the more evaporation you have. So by cooling the reflector you will drop hood temps which will also help to lower your tank temps.
Steve
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