MH Lighting

[FATTIRE280]

I have 2 400 w MH from a previous tank & want to use them on my new 48x30x24. They have 20k bulbs in them......is this correct & what other lighting should I add or use to have ultimate lighting?? Thanks, Roger

[t5Nitro]

2 lights should work, you really don't need anything else because 20k bulbs burn blue. If you wanted an even more ultimate light you should put in 2 actinics.

[michaeldaly]

The two MH lights will be fine, nothing else is really required.

[Wrench]

Actinics are usually used to add a bit of blue light to the tank. Purely aesthetic. Like T5 said, 20k bulbs are pretty blue already. They are rated using the Kelvin scale which means that 10k is pure white. Anything lower will be increasingly yellow and anything higher will be increasingly blue. The 10k bulbs have better PAR (photosynthetically available radiation) which means more useable light will make it to the bottom of the tank whereas the higher K bulbs will have less. This is why a lot of people, especially those with deep tanks, will use 10k bulbs and supplement with actinics so the tank doesn't look yellow. Also, every brand of bulb will have a slightly different color even if they're all rated the same K. If the bulbs are old the color will be different as well. Below are two links that show comparasons of different brands of different spectrum bulbs, both with and without actinic supplementation.

http://www.cnidarianreef.com/lamps.cfm
http://www.coralreefecosystems.com/ltg_bulb_color.htm

[swjim]

Just to add to what Wrench just said, the 20k lights will be quite blue. They should be good for your corals coloration, but because the light will be blue, you may not be able to see all of the colors yourself unless you add some kind of white light supplementation. I would probably add a couple of 10k VHO lights to balance things out.

One other thing, for a 24" deep tank you don't HAVE to go with 400W lights. I realize you already have them now, but you might want to consider selling or trading the 400 halides for some 250s. It could help you with heat issues and power bills. You could even consider T5s if you decide to make a change.

Good luck!

[FATTIRE280]

thanks everyone!! Good Info!

[GSMguy]

lots of sps keepers run 400w 20k on eballast to make them burn bluer and they run actinic sup
to have the ultimate lights i would add 2 or 4 icecap t5 retrofits using 4 pure actinic t5
the supplimented lighting allows you to run the actinics while the halides are off to give a morning and evening cycle

[FATTIRE280]

thanks, GSMguy.......I like that suggestion.