Point source vrs fluorescents total coverage! If you compare the fluorescents cover almost the complete distance across the length of the lamp, this is true for all of them. The point source lamps emits light in a circular fashion off the Length of the lamp inner
fused quartz arc tube and its embedded
tungsten electrodes the light emitted is perpendicular to it & 360 degrees (think I said that right LOL)! These both require reflectors to redirect light where needed as in hydroponics or a fish tank
Some of the fluorescents either use built in reflectors like the URI or the require a reflector external. The good thing about a florescent is you have to make it the entire length of the lamp, it is easy to design a few bends around it which would reflect more light downwards. Now to make my point!
Pendants are typically small, focus point source light in a tight area, penetrating water very deep in the center area but dropping off fast as you go farther outwards. The next type of reflected light from a point source uses the typical spider type design, these are bigger & this allows a larger point area but sacrifices depth penetration slightly. The area covered in most cases is worth the loss in depth penetration for broader coverage but these reflectors have one flaw in their design. The spider type flaw leads to the next reflector in my point, larger & rather than reflective surfaces around the circumference of the arc tube, the Luminarc III's also add the ends to their design & are larger, thus spotting area is larger & you don't loose as much depth as the spiders because they make up for the area loss by adding the extra light gained by the ends being focused into the tank. This is why these LIII's are very highly rated. So if you go with any fluorescents with good reflectors you can do well depending on what you want to keep, & how deep you need the required light. The thing about fluorescents is they last years but what you don't see is how much usable light that corals need is loss much quicker, so changing out 4 T5's compared to one MH may end up in a wash if your keeping sps & the need to have that loss light so you end up replacing the lamps long before they ever come close to burning out. With all that said, considering the amount of electricity consumed I still prefer the MH over the fluorescents but like the fluorescents as supplemental light, pre dawn & dusk light & for colors!
Hanging a pendant leaves lots of open air to help cool the extra heat but it is still required to design some cooling & a UV cleaning schedule & possibly more MH required because of the area they cover vrs a MH with larger reflectors.
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