TANK DEPTH verses LIGHTING

[john rock]

I'm having an issue with coloration which I'm thinking the depth of my tank might be a factor!
I'M using a 14k lamp 400w with 2x actinics,2x 50/50 VHO.
seems to me that I just can't get the color punch I had on my 90g which I ran a 13k PFO.
I try'd the 10k but just not for me and the MH lamp seemed to over power the actinics near the bottom half of my tank.
are XM 10klamps yellow/white or just white?
I realize blue wave lengths travel deeper but could it be that I can't run a 10k [yellowish] lamp on my deep tank. I want color on the bottom for clams etc.
34'' deep minus 3'' of sandbed.

[mickyfin]

Johnny,

Conjecture on my part, maybe someone can chime in with some experience, but I don't know that at the depth of water we're dealing with that 400W 10K lights would have any trouble penetrating 30"-34" of water. I actually think the 10K would penetrate deeper since you get much more light intensity then say a 20K.

Do you think maybe you're just noticing a colouration difference for PFO vs. ARC?

[john rock]

actually what I'm gettint at is not that the MH can penetrate [they do!] its the VHO actinices I'm talking about. see what I'm saying. we add actinics for more color [fluorecing] but at that depth I wonder if they don't cut it as much. nothing serious but just thinking.

[Powder_Blue]

Funny you mention this, I am in the process of setting up a 31" with no sandbed may a 1/2" faux sandband, but I was also thinking about that same issue, what I believe I am going to do is suppliment my 400w 10k with either 175 or 250 20k's.

[john rock]

interesting, I just installed a ICECAP 400W ballast and like the looks of the second MH lamp better. the 14k ARC's are a very nice lamp indeed. I went with the SUPER ACTINIC+50/50 + 14K MH ARC and I think thats just about got it.

[mickyfin]

ahh following you now. I'm sure as the depth increases, the MH do take over the actinic supplimentation much more.

glad to hear you've worked it out :)

[Toutouche]

No experience about the depths and lighting specs, but I would think that VHO's aren't "strong" enough to penetrate your depth if that's what you're finding. Why not mix the 10k's with some 20k's as Powder B suggested?

[john rock]

I try'd that but at my depth the MH lamps looked very different [noticable]. I fired up another 14k ARC on an ICECAP and I'm very pleased.

[Toutouche]

John,
I just thought of something... What length are the actinics that you're "not" satisfied with?

[john rock]

I'm using 2x 4 footers on each side of the tank. I couldn't see fitting an 8 footer in there.

[reeferboy]

How many MH's do you have over your tank?

[Fisherman]

so far 2x 400w on johnnys tank.. 2 more to go lol.

[john rock]

HI STIG, as FISHERMAN stated I have the 2 400w on the left and 8 VHO lamps. I have an electrician coming in next week to add 3 seperate circuits. I have to go about this in a slightly piece meal way as I've already dropped close to $12,000 on this project with many more $$$$ to go. I'm really impressed with the ICECAP MH ballast. I have both 14k ARC lamps on a PFO standard and the ICECAP is brighter for some reason

[Deafboy]

I don't use actinics with my MH, but those who do seem to almost use as much in actinic power as MH power. You have 800 W of MH in there, how many watts of actinic do you have.

I have a pair of 14k ARC (175 W version) over my 72g using the old style pendants. I'm quite pleased with the colour I get.

Michel

[john rock]

440w of actinics. I've found with different setups that the actinics gives it just that little something that MH cannot. ever notice how a tank with just VHO seems to have better color than MH? its because it does. so when you mix both MH and actinics it just rocks. MH gives it that nice shimmer plus the lighting punch corals need as well as reaching the bottom of the tanks.

[Toutouche]

John,
If I were you, I'd go with running 4x 72" actinics ( 160w ea). Remember the old rule: Total wattage of "each" bulb for penetration, not total wattage combined. If they made 84" bulbs, then that would even be better!! To maximize your IceCap ballast, perhaps run 2x 72" actinic and 1x 48" white bulb on 1 ballast?

[Kenzy]

Does a 72" really have that more punch than a 48" VHO? I would think that the extra length would equal the extra wattage and not necessarily mean that it has more punch to reach deeper into a tank. Then again I haven't see any comparisons of the two.

[john rock]

yeh it probally would be easier to run 2 x 72'' on the front and 2 on the back. do you really think that 144'' of lamp [72'']
would still be better than 192'' of lamp [48'']?? I have 2 ballasts so running 2 x 72'' + 1x 48'' [x2 lamps] wouldn't work. not enough lamps space.

[Toutouche]

Well, the 72" bulbs are 160w ea. and the 48" are only 110w ea. Again, it's like running 2x 250w Mh against 1x 400w MH. Which configuration do you think will bleach a low light coral more? You want better "penetration" down to the bottom, right?

[Kenzy]

Your 250 vs. 400w MH comparison is more of an apples/oranges comparison since physically both lamps are pretty close to being the same size and its a single point of light.

With T12 VHO's I don't that it matters if the total wattage is more on a longer lamp or not. In this case I think a watt is a watt is a... so the more the better, but I don't think a longer lamp necesarily puts more light deeper into a tank.

[George]

So Kenzy, what you're suggesting is that a 160W VHO on a 6 foot tank will be the same intensity as a 110W VHO on a 4 foot tank because the extra 50 watts of output difference will be used to cover the 2 foot difference in lengths, rather than a deeper penetration?

Interesting. I think someone needs to grab a good light meter and do some tests!

[Kenzy]

Yep thats pretty much it in a nut shell, and I wholeheartedly agree that some testing would be nice either way. :)

cheers.

[Toutouche]

Kenzy,
It isn't apples/oranges. The way you're looking at it is by adding up the "total" wattage of bulbs running under the canopy. This doesn't work for the penetration purpose. On the 72" bulb, no matter where you hold that light meter,you'll get the 160watt measurement compared to anywhere on the 48" bulb giving the 110W output. A lightbulb shines at a given intensity/brightness no matter at what spot on that bulb you are referring to. The way you're talking about it would mean that the longer bulb would in fact be dimmer at a specific spot on the bulb, or at the very least have the same intensity as the shorter bulb, with the only difference being that since it is longer, more watts are "spread" out over the length. This theory would work if you were talking about filling up that glass tube with beans perhaps and then yes, a bean is a bean is a..., but it would take more to fill it because it is longer and can hold more. But electrons and photons don't work that way.

[Deafboy]

It seems to me that the wattage/inch is pretty constant with these fluorescent bulbs.

110 W/ 48"= 2,3 W/inch
160 W/ 72" = 2,2 W/inch

So I can't fathom how the radiant exittance would be higher with the higher-powered bulbs. In other words, I would suspect that placing a light meter right next to a bulb would give similar results for both length of bulbs.

-40 dB

[Toutouche]

Deafboy,
Again..., you're looking at this as a "total combined wattage in the canopy. The way you're saying this is the same as if you say that a single 250w MH bulb will give the same "punch" in intensity down to the bottom as a single 400w MH bulb, which isn't true. It's not the "spread out" total wattage that counts in this. It's the amount that is coming from the certain point under a certain bulb. If what you're both saying were true, no one would use MH lights and would instead simply install about 50 flourescants under the canopy. Afterall, if you add up 50x any type of flourescant, you'll have a lot of wattage under there..., but it's not going to do anything more down deeper in the tank!!

[frank]

the metal halide bulbs give more intensity to penetrate into the water a 400 will penetrate deeper than a 250as soon as the light hits the water its rays drop quite quick even though the tank looks quite lit anding 500 watts of flouresent will never equal to a 400 in penetration just my opion

[Deafboy]

Whoa there. I never anything that would infer that a 250 W MH bulb will give the same punch as 400 W MH.

I mentioned two things in this post:

- People who use actinic fluorescent with MH seem to almost as power in actinic as they have in metal halide to get the desired effect.

- Two fluorescent tubes of the same type would have the same radiant exittance (light power/length), regardless of the length of the tube. So, a long tube would behave the same effect as two small tubes of half the length.

I understand that a fluorescent tube behave differently than a MH. One is linear source with a diffused coating, the other is more or less a point source. In the case of the metal halide, a properly designed reflector converts the point source into more or less a collimated source. This helps send the power down to bottom of the tank.

Michel

[Toutouche]

Originally posted by Deafboy
Two fluorescent tubes of the same type would have the same radiant exittance (light power/length), regardless of the length of the tube. So, a long tube would behave the same effect as two small tubes of half the length.

Michel,
O.k. I agree on the wording you used in this last paragraph. I wasn't referring to your other points.
You're basically saying that using 1x 6 foot length tube will equal to using 2x 3 foot length tubes, right? But what about if you were using 4 foot length tubes and then switched to all 6 foot lengths. The increased wattage per tube "will" have an improved effect on penetration, right?
Do you agree on this?
Regardless of the watts/inch that you mentioned previously as being consistent with the length difference.

[Deafboy]

Originally posted by Toutouche
Michel,
O.k. I agree on the wording you used in this last paragraph. I wasn't referring to your other points.
You're basically saying that using 1x 6 foot length tube will equal to using 2x 3 foot length tubes, right?



Yes, for tubes placed end-to-end.

But what about if you were using 4 foot length tubes and then switched to all 6 foot lengths. The increased wattage per tube "will" have an improved effect on penetration, right?
Do you agree on this?

There would certainly be more intensity at the bottom of the tank. It is more difficult to access how much more intensity one would get though. The 50% increase in power will not give 50% increase in intensity in the middle of the tank (lengthwise). The increase in would be more significant at the ends of the tank because this is where the added tube length has the most effect. Out of curiosity, I designed a spreadsheet program to calculate the intensity of the 4 foot tubes and 6 tubes in a 6 foot tank. One can enter the depth at which the calculation is done. It is quite instructive. The graph shows the intensity seen at the depth over the length of the tank (horizontal axis). If we input a 2 foot depth (typical depth of tank) one can see that the intensity of the light only increases by 11% in the middle of the tank (lengthwise). OTOH, the intensity is more than doubles at the end of the tank under the same conditions. Inserting other depths in the F3 field calculates the intensity at other depths. Have fun!

You can download the file at

http://pages.infinit.net/deafboy/Intensity.xls

Michel

[Toutouche]

O.k. I played around a bit with the graph. But I still ahven't found a direct answer to my question.
Firstoff, I realize that if you increase the length of a tube installed on a tank, the bigest difference in light would be near the ends because the average person always centers there lights over the tank. When they are longer, they obviously reach the edges closer therefore lighting up that area more. But what I'm asking is about the increase in intensity under the light itself with a light meter. On a longer tube with a higher wattage, the output at any given point directly under that longer bulb should be greater than a point under the shorter tube "because' of the higher wattage output. Or would your argument of the average 2.2 and 2.3 w/ft still come into play here?
As you said above..., "there certainly will be more intensity at the bottom, but how much is hard to tell".
This I realize and I'm not really concerned on knowing exactly how much the difference is. My point is that there just is...

[Deafboy]

The graph shows what a light meter would read at the calculated depth. The horizontal axis shows the light meter reading if we were to measure different positions (in feet) lengthwise along the tank. In this graph the horizontal value of 0 corresponds to the center of the tank. I suggest you try extreme examples to understand what is happening:

- Depth of 0.1 feet: At this distance, it is almost like putting the meter next to the bulb. In optics, one measures in the near field when a light meter very close to the source and that the light meter sensor is much smaller than the source dimensions. Here, we clearly see the effect of longer fluorescent tube. The meter reading is the same for both lengths of bulbs when meter is under the bulb. Obviously, the longer tube has longer span (6 feet) where the light reading is constant.

- Depth of 20 feet: in this case both curves have practically the same shape. This is because at that distance the difference in bulb length has little effect on the curve shape. The offset between the curves shows a 50% increase in intensity between the two bulbs, which corresponds to the 50% power increase given off by the longer bulb. This is called the far field measurement.

If you choose a depth in between these two extremes, the calculation will show a combination of both effects (different tube lengths and differnce in power btween the bulbs). I hope this answers your question.

-40 dB

[Toutouche]

Yup!!!

[badmedicine]

You guys lost me early!

The depth of the water is "28" for my 180gal. Do I need 400 watt or 250watt. I am thinking 3 lights over the tank. What do you people think? 250watt or 400 watt I want to keep my options open regarding what corals to add.

To confuse the issue even more....
Can I use 1 400 in the center and 250's on the ends if need be?
Separate actinic lights ( another issue)
Thanks!

[Toutouche]

The depth of the water is "28" for my 180gal. Do I need 400 watt or 250watt.

It depends on the types of corals you want to keep. Also, what types of lights you want to use. Single ended or double ended?

I am thinking 3 lights over the tank. What do you people think?

What is the length of your tank? Usually you have 1 light for every 2 feet.

250watt or 400 watt I want to keep my options open regarding what corals to add.
As I said up above, it all depends on the types of corals you want. Will you be going with SPS? I personally am now thinking you don't really need 400w bulbs, even on a tank such as mine which is 30" deep.

To confuse the issue even more....
Can I use 1 400 in the center and 250's on the ends if need be?

Yes, many people do this.

Separate actinic lights ( another issue)

IMO, definitely!!!! The more the merrier!!

Thanks

No problemo!! :D

[badmedicine]

Okay thanks!
I am kind of partial to these fancy HQI setups. They have actinics (VHO), HQI x 3 and some Moon glows all in one unit (with three power cords).

I am sorry I should have stated that I am using this lighting over a 175 bow that is 6 feet long.

My chalenge is to narrow my "wants" down.
Thanks for your help!

[ReefSalt]

Hey J.R

I use the XM 10k`s they are a white light,if you are used to 14 or 20 you will find them yellow.

If you go to XM`s site or even sanjay`s lighting pages and do a spectral analysis on the 10k you will notice that the 10k`s have a high spike at 420,thats probably why a few people noticed great coloration.

Spectral analysis XM (http://www.advancedaquarist.com/issues/aug2004/review.htm)

[LT Hook]

If you compare bulbs and kind with your eyes, then it’s about personal taste.

Light penetration must be compared in the same wavelength. No sense on comparing a daylight and actinic, not the same apple.
Just like my 25W T8 Stay bright, much brighter at the bottom of my tank (brighter to the eye) then my 95W VHO actinic. Not the same apple.

Data from San Jose state University (natural sunlight)
Intensity of light decreases rapidly with water depth, for example,

only 73% of the surface light reaches a depth of 1 centimeter (less than a half inch)
only 44.5% of the surface light reaches a depth of 1 meter (3.3 feet)
only 22.2% of the surface light reaches a depth of 10 meters (33 feet)
only 0.53% of the surface light reaches a depth of 100 meters (330 feet)
only 0.0062% of the surface light reaches a depth of 200 meters

Light wavelenght and depth,
up to 2300nm surface
up to 1400nm 10CM
up to 800nm 50cm
420 to 520nm 100m

My 2 cents.