Lighting Question

[hank]

Well I thought I'd made a good choice, but the more I read the more confused I am. I have a 72g bow front tank, fish with some soft corals and an anemone. I just bought 2 Current Sundial Pendants, each has 150w HQI and 2 actinic. The tank being 24" deep, I'm concerned that 150 may not be the right choice. Any thoughts would be appreciated.

[charlie]

Probably should have gone with at least 250W, but then again, what types of corals are you going to have?

[Ninong]

You will be fine with the 150w size. Just make sure that SPS and crocea or maxima clams are placed directly under each fixture and at least halfway up the rock structure. This is assuming that you intend to keep a mixed reef.

If you're going to keep mostly SPS, then you can experiment to see what will adapt to lower placement in your tank. Crocea and maxima clams should always be placed on a rock substrate anyway and it would be better if these were located directly beneath a pendant and at least halfway up.

These pendants came with 10,000K 150w lamps and I wouldn't change those for anything like 14,000K or 20,000K because that would reduce your PAR too much. I'm not familiar with the brand of lamps they used but you could always replace those 10 months from now with one of the 150w 10,000K lamps that we know from Sanjay's testing to be very good lamps.

And, just for the record in this thread, they also came with two 32w dual actinic PCs in each fixture and automatic timers in each fixture.

The owner's manual recommends 9-10 hrs/day for the metal halide lamps, which I agree with, but it recommends 10-11 hrs/day for the PCs. I would make that 12 hrs/day for the PCs.

Maybe I will go find some photos of tanks larger than yours that are thriving with just 150w metal halides just to make you feel better about your choice. It's amazing how corals, including SPS, can adapt to variations in lighting. Besides, some 150w 10,000K HQI DE lamps put out as much, if not more, PAR than some 250w 14,000K or 20,000K HQI lamps.

Good luck!

[Ninong]

I forgot to mention that you should locate the lamps as close to the water's surface as you can and still get good light spread. Obviously this distance will vary depending on the front-to-back dimension of the aquarium. In your case, you might be able to locate them 8" above the surface but you would have to see what's best. If your tank had a 24" front-to-back dimension (which it doesn't), then you might have to position them at least 10" above the water.

See what provides the best coverage, both front-to-back and across the full length of the tank. I think 6"-8" might work. See what you think.



P.S. -- If you have a standard glass 72-gal bow front tank, then it's 48"L x 18"W x 22"H. And that's 18" in the middle of the tank, not the ends.

Your water column would be around 20"H, at most, assuming a bare-bottom aquarium, which I don't care for myself. So, assuming your sand bed is at least 2" deep, then your water column is less than 18", which is another reason why the 150w lamps will be adequate (IMO).

[Ninong]

I want you to look at this tank: RC's Feb. 2005 TOTM.

Tank
The tank is an all-glass tank of 130 x 70 x 70 cm, containing about 160 gallons. (That's 51"L x 27.5"W x 27.5"H).

Lighting
Light is provided by an Aquaspacelight with two 150-watt HQI bulbs and two 24-watt power compacts. The fixture is about 5" above the water's surface. The HQI bulbs are BLV Hitlites; the power compacts are typical blue bulbs from Osram. I change the bulbs yearly. The HQI's are on for 12 hours/day, and the power compacts for 13 hours. I've been using 150-watt HQI bulbs for about nine years now, and I'm very satisfied with this way of lighting the tank. In the very beginning I used 6500K bulbs, because nothing was available with a higher Kelvin rating. Later, I switched to Aqua Medic 10,000K bulbs. This year, I decided to try the BLV bulbs. These bulbs weren't developed particularly for our hobby, and compared to the Aqua Medic bulbs, they lean a little more toward the blue part of the spectrum.

I used 250w 10,000K HQI DE lamps and I did exactly the same thing as that guy did: I started out with AB (Aqua-Medic) 10,000K lamps and then I later on switched to BLV 10,000K lamps. I liked the BLV (Ushio) lamps a little better because they appeared to me to be just slightly more bluish-white than the AB lamps.

I want you to notice that his tank is much wider and much deeper than yours and yet he has lots of SPS, even all the way down to the sand bed. He's also keeping his fixture a lot closer to the water's surface than most people would. In fact, the manufacturer of his fixture (Aqua-Medic) insists that it should not be kept any closer than 30cm (11.8") from the surface of the water. I kept my Aqua-Medic fixture 11" from the water's surface but I know that most people keep them around 8".