distance between MH bulbs
- Thread starter jead85
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which reflectors are you using
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12" between the reflectors I would think just not familiar with how they spread. That is only an opinion.
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Also consider your rock placement as well in relation to the placement of your lights. Kinda limited on a 48" tank .
With my 120, john and I measured how far over it would be to center each one up over each bay on top and went from there..
That way its directly over the opening and evenly lit on each side..
That way its directly over the opening and evenly lit on each side..
Most metal halides have a 2 foot spread. The other factor you have to consider is the height at which the halides are mounted from the surface of the tank. The higher the distance the greater the spread of light and the greater the par produced to a certain height. This results from the overlap of metal halides as they are raised from the surface of the water and in turn you can let your distance increase between the lamps. There was a great article written by lee on reef keeping magazine not too long ago..i'll see if i can dig it up.
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Have you considered any possible heat issues ?
Most linear lamp reflectors (your kind) produce a parabolic distribution pattern out the 'sides' (short dimension) of the reflector. So, the long dimension of the reflector SHOULD be perpindicular to the length of the tank. A LOT of people don't do this, and it is a mistake-IMHO. Of course, if the reflector length exceeds the tank width, then that limits the options for mounting.
You can mount the lamps at positions 14 inches from the ends of the hood. This will give you a 20 inch separation between them, in the middle of the tank (assuming a 48 ich long tank). The parabolic spread pattern will overlap, in the middle of the tank, by an amount determined by the height. The higher you raise them, the more they overlap, but the more you will lose out the ends of the tank too. Space them at the distance above
l-14-20-14-l inches
, and raise them off the floor in a darkened room untill you get an overlap between them that appears to be uniform over a 48 inch distance (that will represent the bottom of your tank). This will give you an idea of how far from the bottom of the tank to mount them. You can use parallel strips of masking tape 48 iches apart on the floor, to represent your tank bottom during this experiment.
BTW- the reason that the separation distance is not equal is that where the parabola from the two lamps meet in the middle, the lamp output will combine to give a higher irradiance than either lamp alone. This does not occur on the ends of the tank, hence this 'offset'.
Below is a link showing what a parabola looks like. As the saying goes, "a picture is worth a thousand words".
http://en.wikipedia.org/wiki/Parabola">http://en.wikipedia.org/wiki/Parabola</a>
Page down untill you see the 'Parabollic trajectories in a fountain'. This is kind of what the light pattern will look like from the front or back of the aquarium, [B]<u>IF</u> you mount the lamp so that the length goes from front to back of the aquarium (not lengthwise)[/B]. The fountain surface would represent the bottom of the aquarium in this instance. Hope this helps. -JMHO
You can mount the lamps at positions 14 inches from the ends of the hood. This will give you a 20 inch separation between them, in the middle of the tank (assuming a 48 ich long tank). The parabolic spread pattern will overlap, in the middle of the tank, by an amount determined by the height. The higher you raise them, the more they overlap, but the more you will lose out the ends of the tank too. Space them at the distance above
l-14-20-14-l inches
, and raise them off the floor in a darkened room untill you get an overlap between them that appears to be uniform over a 48 inch distance (that will represent the bottom of your tank). This will give you an idea of how far from the bottom of the tank to mount them. You can use parallel strips of masking tape 48 iches apart on the floor, to represent your tank bottom during this experiment.
BTW- the reason that the separation distance is not equal is that where the parabola from the two lamps meet in the middle, the lamp output will combine to give a higher irradiance than either lamp alone. This does not occur on the ends of the tank, hence this 'offset'.
Below is a link showing what a parabola looks like. As the saying goes, "a picture is worth a thousand words".
http://en.wikipedia.org/wiki/Parabola">http://en.wikipedia.org/wiki/Parabola</a>
Page down untill you see the 'Parabollic trajectories in a fountain'. This is kind of what the light pattern will look like from the front or back of the aquarium, [B]<u>IF</u> you mount the lamp so that the length goes from front to back of the aquarium (not lengthwise)[/B]. The fountain surface would represent the bottom of the aquarium in this instance. Hope this helps. -JMHO
