halides vs. power compacts

[andrewbrichards]

i am starting a 90-gallon reef, and i am a little stuck on whether i should go all halides, or a combination of halides and power compacts. i found a killer deal on 175-watt halides, and i will for sure get two. that gives me 350 watts. my goal is to have at least 5 watts per gallon, if not more. i would like to be able to house hard corals, as well as clams and other high light invertabrates. so, i am not sure whether i should use two more halides, giving me an end product of 700 watts, or a little over 7 3/4 watts per gallon; or if i should just use two 175 watt halides and a 260 watt power compact unit, giving me a little over 6 and 3/4 watts per gallon. i was reading the other day that one should not have any more than one halide per two square feet of aquarium surface. is that true? i really like halides because of the rippling affect which is both pleasing to look at, and more beneficial to the photosynthesis of corals. but i don't want to have too many halides, if there is such a thing. so what should i do?

 

[Skimmy]

in a 90g reef, i would probably be thinking more along the lines of 250w - 400w m.h. w/ v.h.o. actinic, unless your good deal limits you to 175w, i dont see how having 3 or 4 175w bulbs in a 4" canopy is going to be bad other than a possible heat issue, i've seen it in many canopys before, but it might require a chiller or small air conditioner for the room the tank is in, and several fans inside the canopy. fall thru spring wouldnt be too bad probably, you might be able to get away with just fans.

 

[andrewbrichards]

yeah, my good deal is only on 175 watts. also, i don't have a canopy, so that will help dissipate the heat much faster. if needed, i will place one or two fans blowing across the lights, and probably another one or two underneath the tank in my sump, as my pumps generate alot of heat as well. so having 4 halides would work alright?

 

[Kensn]

Well I guess with 2 175w MH, and 2 110watt Atinic vho's you would have 560 watts. If you use 6500k bulbs you might get a good par rating compared with higher kelvin bulbs, and the atinic will take all the yellow out of the look. See my home page for an example of that look, I run 2 250wt 6500k mh and 2 vho atinic. I know the higher kelvin bulbs are the rage but if your going to run atinic you really don't need the higher kelvin IMO.

 

[jennyclark]

I agree with Ken. Two 175w halides and some vhos or pcs will be plenty. Personally, I like pcs better than vhos. Just my opinion.

 

[ninerfoelife]

You should go with the 2- 175watt halides, and some vho's. 4 metal halides would cause a lot of heat.

 

[clayswim]

The problem with using PCs in a tank that deep is most of their light won't penetrate to the depths of the tank. It would be fine for anything near the surface of the water, but many inverts prefer it on the bottom; like clams for instance. T5s are a little better, and VHOs are better yet. You could always opt for one more halide and space them evenly. That would give you 525 watts.

Clayton

 

[wrightme43]

Or you could try to find another good deal on some 250s or 400s With a tank as deep as 90 a 250 is really the min to punch deep enough to be of real use. I have 2 250s on my 75 and I wish I had went with 400s.

 

[andrewbrichards]

yeah i am kinda leaning towards 400 watt halides now. the halide i was looking at was actually at home depot. they have a complete fixture, ballast and all, for about $85. however, i would need to swap out the bulb included, because the one in the fixture is probably only about a 3300 k, which obviously is not a great idea for a reef. the fixture looks like a flood light that you would find over a driveway or over a parking lot. they only have this style light in 175 watt. the 400 watt halides look like a light over a gym; they are shaped like a bell, and the ballast is mounted in a white plastic box. i could just hang these over the tank from my ceiling. i was thinking of going with 14000 k bulbs. that brings me to my next question: with a large halide fixture such as this, how high should i suspend the lights from the surface of the water? my tank is 24 inches deep, and i read that one general rule is 35 inches from the bottom of the tank. another source says to hang them one foot above the surface. what should i do?

 

[clayswim]

Check out http://www.hellolights.com/

They have lighting parts pretty cheap, including a 400W retrofit (without bulb) for $89. It has an external enclosed ballast and a reflector.

Hang your light at least 12" from the surface to cut down on heat and minimize the risk of splashing water hitting the bulb. With a 400W it's sometimes necessary to place them 18" above. You don't have to worry about losing too much light in that space, since light travels much easier through air than it does water.

Clayton

 

[wrightme43]

Here is another tip I learned the hard way. A good reflector is well worth every dime spent. Another place to look at is cooltouchlighting on ebay. Less than 350 in this.

 

[Skimmy]

oh yeah, wrightme43, aint it the truth?
andy, check out "diamond lumenarc reflectors", super sweet!!

 

[mungus]

Here is a link I found interesting. http://aquarium.union.rpi.edu/articles/DIY_MH.html
If you used a setup like this you would probably want to go with an additional 2 atinic VHO's for color. I am going to use this setup once I get my prop tank up and running.

 

[Kensn]

That is the article that inspired me. I went with electronic ballasts though.

 

[andrewbrichards]

you guys are awesome. thanks for all of the excellent help so far! ok so a couple more questions: what is the difference between probe start and pulse start? i know they are both "older style" ballasts, and that electronic ballasts are supposed to be better and more efficient, but what else? knowing that i would like to do sps, clams, etc., should i do two 400w, or would i be better off just doing 250w and using some supplemental lighting? i would like the lighting to be cheaper, and obviously if i use two 400w halides, that's all the light i need; while the 250w would give me a solid 5wpg and i may want/need to add more. ok so all of you who do have sps, what are your watts per gallon? i know that that isn't a very accurate measurement, because it's more the intensity that matters, but for the sake of not having another way to measure...

again, thanks for all of your help!

 

[clayswim]

Pulse start ballasts have igniters and probe start ballasts don't, that's the only big difference. Although it may be possible to run one type of lamp on the other type of ballast, you run the risk of having lamps that won't always start and perhaps even burn out early. It's best to match ballast and bulb, or use an electronic which will run all of them.

There's an ongoing debate as to whether or not electronic ballasts are better than magnetic. Electronics for the most part are better. They run cooler, they run quiet, they can start any type of halide lamp, and they tend to be more power efficient. What they might not be, however, is reliable. When they first came out electronic ballasts were horribly unreliable, burning out sometimes in a matter of months. They've gotten much better in recent years as long as you stay with the better brands; but most companies still choose magnetic for commercial and industrial use because of their proven track record. For our purposes I think either one is a good choice.

On a 90 gallon for clams and SPS I would definitely go with 400W. The ballasts and bulbs are only a few dollars more than 250W, and with a 24" deep tank you need plenty of light to penetrate the water. Watts-per-gallon is an old, but still often used rule of thumb. Unfortunately it means very little. When sizing a tank for light there's only two things to consider; tank depth and length. Depth will determine the wattage of the lamps, which for 24" would be an absolute minimum of 250W; but 400W would be preferable. Length (and width) determines the number of lamps used. For the most part you should have one lamp every 24". In your case this would mean two lamps.

Clayton

 

[andrewbrichards]

i also read in the article shown to me by mungus that pulse-start ballasts tend to hum during operation, while the other types of ballasts do not. i think i will go with probe-style ballasts, probably two of the aro cubicus retrofit 400w from hellolights.com. will it be necessary for me to use a uv shield between the lights and the tank? i am planning on setting them up 12" from the surface of my tank, if that makes a difference.

 

[clayswim]

Both probe and pulse ballasts have a hum, that's unfortunately part of having a magnetic ballast. Only the electronic ballasts are completely noise-free. I've used halides both with and without UV shields (basically any glass or acrylic sheeting). The only reason I usually use something is because of the risk that water might splash on the bulb causing it to blow-up. That's never once happened in all the years I've used halides, but I'd rather be paranoid than have bits of hot glass everywhere. The 12" does make somewhat of a difference, especially for the more potent UVB. Some people claim though, and could be right, that the huge amount of UV rays created by the halide lamps can have a negative effect on corals even if suspended high. For some deep water corals this may very well be true since on a natural reef the UV rays have already been filtered out in the water at their depth. A shield also helps protect the tank from the heat. Just be sure to use a fan to cool the lighting fixture down.

Clayton