questions about 20K HQI metal halide bulbs

[singlejm]

I just ordered a aqua medic 250watt 20000K HQI pendant and have a few questions. Will these kelvin rating inhibit me from keeping certain corals since it is extremely blue. I really don't have the ability to supplement actinic so that is why I opted for the 20K vs. the 10K. My tank is 56 gallon column tank that is 30"L 18"W 24"H. Any opinions or advice on this bulb would be appreciated. Right know I just have mushrooms and zoanthids which will be moved all the way to the bottom, but how high off the tank would you recommend me mounting the pendant. I hope itn isn't going to be insanely blue but i didn't think i had much choice since i don't really have any room for actinic. One last ? My tank has a center brace and i know i am going to block a little bit of the light with it but should i be concerned about the heat from the bulb possibly melting it and should i remove my glass tops when using the halide or leave them on.
Appreciate any opinions

 

[Len]

20K bulbs all tend to produce lesser light output (PPFD) compared to lower kelvin bulbs. Aside from reduce intensity, the color temp itself is usually not a problem, although some corals will produce different pigmentation compared to being lit by lower K-rated bulbs.

The pendant should be mounted 6-12" above the tank depending on your desired spread. If you don't mind having less light on the sides but want stronger intensity in the center, mount it lower (and vice versa).

If you don't have any jumping fish, I'd definitely remove the glass top to allow your tank to breathe, cool, and get the maximum amount of light. The center brace, if it is glass, will not melt. If it is acrylic, it might warp, but unfortunately most acrylic tanks with center braces require the brace to maintain integrity.

A good bulb for you to consider is the Phoenix 250W 14K DE. It is very nicely blue but produces a lot of PAR. I very much like this bulb.