newbie lighting question

[ziah]

I just purchased a used tank with a custom built canopy. The lights installed "under the hood" is 2 NO 40 watts and 1 MH (I think it's a 175 watt bulb rated at 10000k).

Will this lighting be enough to support soft coral and maybe some hard coral? Also, can I get a new 175 watt bulb rated at 20000 and work with my current ballast?

BTW, the MH was a DIY job with parts from an industrial lighting place. Not sure what the differences are since I've never seen MH lights sold at pet stores. I assume the bulbs from a the pet store will screw into my industrial grade light socket. Please correct me if I'm wrong.

Thanks,

Ziah

[afss]

you should be able to keep almost any coral you want in the tank (depending on the tank dimensions) as far as lighting goes. You may also be limited by the rest of your set up as far as filtration skimming etc, (your water quality control)

Scott

[afss]

Forgot, you should be fine to go with a 20k bulb on the balast.. its the wattage that matters, not the color spectrum

Scott

[pbutkovich]

20,000K is really blue isn’t it? What advantage would there be in switching from 10,000K which is close to natural levels to something that High? What size is the tank? The metal halides will cover an area of about 2 square feet so all corals needing high lighting would need to be kept within this two foot halo.
Paul

[Chrismo]

You should check to see what wattage your Metal Halide ballast is before you buy a bulb... A 175Watt Ballast will only work with a 175watt bulb.

That 20,000K bulb you are talking about isnt a better bulb, it's just different colour. It's Bluer. You might find it is much cheaper to make your tank look blue by switching your NO bulbs for Actinic(=blue) bulbs. As long as your bulbs are 6,500K or higher they are fine, anything else is mostly aesthetics. Personally, I think 10,000 is blue enough.

You are set up pretty good for soft corals, and probobly hard corals in a 2~2 foot area under your bulb. So depending how wide, or deep the tank is, your mojo may vary.

Chrismo

[johnfish]

Hi Ziah,

Depends a lot on the depth of the tank and how high the bulbs are above the water. The intensity of the light is only one quarter every time you double the distance (inverse square law).

A 175W like six inches off the surface would be good to 12 or maybe 18 inches deep. It should cover a footprint of about 2 feet square. Great for soft corals, might be a bit low powered for hard corals.

The 20,000k bulbs look about half as bright as the 10,000k. I have two 400W 20,000k bulbs over a 45 gal and it looks just right. One bulb looks dim. A single 10,000k is plenty bright.

I think if you put a 175W 20,000k in, it will look really dim and probably not grow coral very well. Stick with the 10,000k if it is fresh. The Iwasaki 6500k grows coral really well, but looks kind of yellow. Upgrade the actinics (see below) and it will compensate for this somewhat. This is a popular combo.

You ballast should be an ANSI M57 I would guess. That is a plain, ordinary 175W Metal Halide ballast. If it says M57 on it, you are safe. The bulbs from the petstore will definately run with the correct industrial ballast.

If you want to upgrade the actinics, get a Workhorse 7 Electronic industrial ballast (about $70 from Litemore Distributors in Toronto) and run two VHO actinics. They will give you two or three times the output.

Cheers:)
John