Help, lighting question

[minitrucker]

Does the total watts from both the MH and the VHO Actinic count towards the total watts per gallon for the tank?

I am going to buy lights and don't know if it is better to buy 20,000k MH bulbs which make the tank look better or get 10,000 k which are better for the corals. I also have 2 VHO Actinic tubes that I dont know the wattage of. Do the watts from the Actinic bulbs add to the watts from the MH to equal the total watts for the tank?

[minitrucker]

ttt Anyone??

[hahnmeister]

Watts per gallon can get you into some trouble.

A better way to do this would be to tell us what size reef you want to keep, and what things you would like to keep inside of it. Soft Corals, SPS, LPS, clams, zoas, polyps, shrooms...etc?

[minitrucker]

Well my Dad posted this under my name. I have told him about the watts per gallon "rule". Can you please elaborate as to why it may get him in trouble? This way he gets at least 2 opinions on the subject.

[hahnmeister]

Uh, *$#%#!, the reasons are endless...where to begin. It just isnt done...

For one, wattage tells very little about how much PAR (check Sanjay's article in the new Reefkeeping issue on lighting for more on that) is being made. A 20,000K halide bulb often makes 1/2 the PAR of a 10,000K halide...and a halide makes more PAR per watt than say...a power compact bulb.

Now, even with PAR/gallon...there is trouble. Lighting really depends on what you want to keep, and where in the tank you want to keep it. Put it this way...1000watts over a 10g does little for the coral that gets placed in a cave. Lighting the rest of the tank is much like this. The height of the tank will change things...a 30" tall 150gallon might need three 400 watt bulbs, but a 20" tall 150gallon might only need 250watters. A long narrow tank vs. short and fat...etc. You can also have varying zones in the reef. You might place a 400watt bulb in the center, and 250watters at the ends for different corals. You could get away with only a single 250watt halide over a 125gallon if all the corals were at one end...

The only accepted method of calculation that I know of for lighting is a measure of PAR or lumens per square unit of measure (inches most likely). This measure at a given depth can be used as a basis of comparison from tank to tank as a way to really measure the light that a specific part of the tank gets...and this is what is important.

Im tired, so Im sure that isnt the best way to word it...but with very few exceptions, watts/gallon is not a good idea.

[minitrucker]

Thank you very much for that. Ill have him read this.

Thanks again

[hahnmeister]

Well, I have my wits about me now (late afternoon as compared to middle of the night), and I remember the best example...

Going by watts per gallon gets you into trouble because its not the wattage or output even, but how you apply it. And I dont just mean using a good reflector on T5 bulbs vs. the 60% you lose w/o a good reflector. I have seen a 150g with nothing but two 175watt bell pendants, and I had a 10g with a 250wattDE 10,000K over it for clams & sps.

You will find that the larger of a reef you go, the less the wpg you need as well. "How's this?"...well, a large reef can have larger 'dead spots' and still be fine. On Energy's 1700g stingray reef for instance, he has all his corals in two central rock clusters, and the rest of the tank is open swim space for the fish that he doesnt need to light. And like I said before, a 150g with only 2 175watt bell pendants was growing all kinds of corals from softies and xenia to sps. Thats like 2.3 wpg. Now, at the opposite end of the spectrum, lets say you have a 5g that you want to grow SPS &clams in, and you use that same wpg ratio as a large SPS tank like the 1700g reef...something like 5 watts per gallon. That means only 25watts?!?! Yeah, try growing a tort or clam under that. With a large tank, you have more strategic placement opportunities on your side...not so with a smaller tank.

You could run a 55g long with dual 250watt halides, and extra VHO actinics, and my 60g cube with a single 400watt lumenarc pendant would provide more light even though the wpg would be lower. Why? Well, what do you think is brighter? Being an average of 6"-12" away from a 250watt bulb or a 400watt?

The best way to do it would be to list your tank dimensions, and your intended inhabitants here on RC in a thread (or look at others with similar tanks and critters) here on RC, and have people chime in and give suggestions. You will find a huge variety in possibilities.

A 55g can be run with dual 250s...this might sound high, but a 55g is a tall tank. A better option at that would be a 75g, which could be run off of the same lighting (the 75g is actually shorter by 2", and has an extra 6" of front-to-back depth which is going to get the same light as the rest of the bottom when you think about it. OR, you could run a T5 setup. A 4-6 bulb T5 fixture would light up a 55g very nicely.