Lighting Suggestion for 100g

[The_Macs]

So I've been trying to plan out my 100 gallon build. I figured out my pumps/sump/overflows etc, and am on the lighting. I want to be able to keep pretty much anything except sps. The tank is 72"Lx18"Wx18"D. I'm settled on t5 lighting, but don't want to spend much on a fixture. So I've decided to DIY a fixture. I'm wondering how many bulbs I need. I plan on using 39w T5ho which are only 34" long, so I'll need 2 bulbs to fill the length of the tank. I'm also planning on using the Fulham line of Ballasts, the WH5 and/or WH7.
The WH5 can operate up to 3-39W T5HO bulbs, the WH7 can operate up to 4-39W T5HOs.

So here are my options

Option 1
1 WH7 ballasts
Total of 4-39W bulbs
(future upgrade: add another WH7 ballast and 4 bulbs)

Option 2
2 WH5 ballasts
Total of 6-39W bulbs
(future upgrade: add a WH7 ballast and 4 bulbs)

Thanks in advanced

[charlie]

Go with option 2 but if you want clams, you may want to upgrade sooner, depending on the type of clam you want. Do some reading on the types of clams and their lighting requirements, OK?

JMHO

[Ninong]

Do not go with Option 1. All you would have would be one 39w daylight and one 39w actinic over the tank in any one spot. That one's a non-starter unless you're doing a fish-only aquarium.

Option 2 would give you two daylight and one actinic over the tank in any one spot. That would work for some softies but not LPS or SPS. I would go with Option 2b from the beginning: 4 tubes over the tank in any one spot -- two daylight and two actinic. That would allow you to keep softies and LPS. You could keep some SPS if you choose the best location for them. You might be able to keep Tridacna maxima clams if they are located high on the rock structure.

Obviously the best option if you expect to keep SPS and clams would be Option 2c: six tubes over the tank in any one spot, half daylight and half actinic. That would give you 117 watts of daylight and 117 watts of actinic over each side of the tank. That should work for just about anything because your tank is only 18" tall.

Unfortunately, a tank that is 6' long requires a lot of T5 tubes to cover it because they don't come larger than 5' in length. A 5' long or 4' long tank would be easier to work with because the T5 tubes come in those sizes.

[The_Macs]

Thanks for the help Ninong.

Is this assuming that they have individual reflectors?

I guess in the end, the most cost effective would be to go with a WH7 for now and add another WH7 when possible and not keep any corals until I have all my bulbs. Right?

If I wanted to go ahead and have corals now, would I be okay with the 2 WH5 ballasts with 3 bulbs over any one spot? That way I can keep the few zoas and palys I have now...? (they are in my 2.5gallon pico reef tank)

Sorry to ask so many ?s, but I know you said 6 bulbs over any one spot is good for SPS, but will 5 do?

Thanks again for all the help

[Ninong]

T5 tubes are adequate for anything over an 18" tall tank provided you adequately cover the tank. If you were purchasing a ready-made fixture, that would mean that the fixture covers about two-thirds of the top of the tank.

Several years ago a test was conducted to measure the intensity of T5 tubes (meaning the amount of light reaching the corals) with and without individual reflectors. It was found that T5 tubes with individual reflectors performed much, much better than sticking all of the T5 tubes in an enclosure with just a white painted surface or just a single aluminum lining. There was a really big difference. That's why everyone recommends individual reflectors.

When using T5 tubes, most people choose a mix of 'colors' instead of just half daylight and half actinic. Of course that all depends on how many tubes you have covering the tank.

Anyway, you need more than just two or three T5 tubes spanning the space from front to back at the top of your tank. I would go with a minimum of six on each side of the tank. I guess you could do half now and then add the other half later on.

[Ninong]

Check out this guy's tank. That will give you an idea of the possibilities with T5 lighting. That fixture has ten 5' long 80w T5 tubes. It's also VERY expensive.

[The_Macs]

I've seen fixtures sold with 4 bulbs across. I know I want softies (zoas/palys/mushrooms/etc)...not too big a fan of LPS, but later (MUCH later) I'll try to upgrade to have 8 bulbs across and do some SPS. If I did 4 bulbs across, what corals would I be able to support?

[Ninong]

I've seen fixtures sold with 4 bulbs across. I know I want softies (zoas/palys/mushrooms/etc)...not too big a fan of LPS, but later (MUCH later) I'll try to upgrade to have 8 bulbs across and do some SPS. If I did 4 bulbs across, what corals would I be able to support?

Think of it this way. It's not the number of bulbs at all that matters. All that really matters is the intensity of light incident on the surface of the coral. What that means is that if you place a particular coral 12" beneath the surface in the middle of your tank and your 4-bulb fixture is directly over the center of your tank, that coral is likely to receive almost as much light as a similarly situated coral in a tank with a 10-tube fixture, assuming decent individual reflectors.

It's just that you need a certain number of tubes to adequately cover the exposed surface area of any tank. And you need a certain intensity of light for a certain duration (photoperiod) to satisfy the photosynthesis needs of the various species of corals that you hope to keep. I don't think you can even come close to this objective with just two tubes over any given part of the tank. I think you can do any adequate job with four tubes and a much better job with six tubes. I can't predict accurately what you can keep without taking a luxmeter (or even better, a PAR meter) reading at a certain distance beneath the light fixture. The size of your tank doesn't really matter. The distance between the coral and the light is what matters more than the size of the tank. That's why the height of your tank is important. It's a lot easier to light an 18" tall tank with T5s than it is to light a tank that is 28" tall.

With four tubes over your tank (at each end), you may be able to keep some SPS provided they are positioned high on the live rock structure and directly beneath the light fixture. Again, a six-tube fixture would be better but that's up to you. At least four-tubes (over each end) is a whole lot better than just two.

Good luck!

[The_Macs]

That makes a whole lot more sense! Thanks for explaining that to me Ninong. So...to keep SPS I don't need to light up the whole tank...I would just need to know that I have enough light over where I want to keep an SPS coral and place the coral high enough that it gets as much as light as necessary. So the theory is the more light coverage I have the more photosynthetic demanding corals I can keep.

With that being said I know I'll go with the WH7. I'll figure it out later, but I was told the WH7 can run 4 -54W T5HOs, so I would just stagger them. If I have the money I'll try to at least buy the standoffs and endcaps so the upgrade would be easier and I wouldn't need to rework the layout so much. That way I could be able to keep some softies so long as I place them correctly?

Now someone else in my local reefclub had brought me to a site that sells commecial t5ho fixtures. I'm thinking that maybe I can buy one of those fixtures and gut it, then add a WH5 ballast to run some 24" t5ho lamps to get my 6 feet of coverage. Anyone know if this would be a bad idea and why??

[Ninong]

Most soft corals are capable of adapting to strong light. So strong light is very seldom a problem for them. On the other hand, while many SPS are capable of adapting to a wide range of light intensity, there really is a minimum intensity necessary for them to live long and prosper. The same goes for tridacnid clams, especially T. crocea.

Any animal that harbors zooxanthellae requires a certain intensity of light for a certain daily duration (photoperiod) to power the photosynthesis process in the zooxanthellae. This minimum light requirement varies greatly between species of animals.

There are three terms used to describe the light intensity when discussing photosynthesis: compensation point, saturation point and photoinhibition point. The compensation point is the point below which no growth takes place. The saturation point is the point above which additional light will not result in additional growth. The photoinhibition point is the point at which photosynehesis will begin to shut down because of overload.

In an ideal world you would want to provide your photosynthetic corals with enough light to approach their saturatiion point. That rarely happens and it is totally unnecessary. What is necessary is that you provide corals with substantially more light than their compensation point if you expect them to survive and grow. Unless you decide to stick a 1000w metal halide lamp 12" above your tank, you are not likely to have to worry about the photoinhibition point ever being reached much less exceeded.

I am more familiar with the light intensity readings below a 250w metal halide lamp than any other type of lighting because that is what I used over my aquarium and therefore it is what I researched. However, the general principles are the same regardless of the source of the light, except that fluorescent light is not point source light and it is distributed along the length of the tube. With any fluorescent lamps, the light is dimmer for the first few inches at each end of the tube.

However, rather than turn this into a lengthy article on light, let me just say that your strongest light will be beneath the center of the tube and the overall strongest light will be beneath the center of the middle tube in the fixture. The dimming that I am talking about takes place in the first three or four inches at either end of the tube. As you move away from directly beneath the outer tube, your light will drop off dramatically. That's the reason it's a good idea to cover say two-thirds of the top of the tank when using fluorescent lamps. This is just a guess on my part but I would guess that the light directly beneath the middle of the fixture is more than double the intensity of the light directly beneath a spot that is 6" outside the outer tube even when using excellent reflectors and positioning the fixture an appropriate height above the tank to achieve optimum light spread.

We can also estimate that the light intensity 8" beneath the water's surface will be double the light intensity 16" beneath the water's surface. We would need to know the exact distance of the lamp above the water's surface to come up with any real numbers but I'm just trying to give you a general idea of the difference placement makes inside the tank. Also, the light intensity at 16" beneath the water's surface directly beneath the center of the fixture will be much stronger than the light intensity 16" beneath the water's surface 2" from the front glass. I haven't even touched on Kelvin ratings and that too makes a huge difference. If you're really interested in reading up on how light intensity drops off depending on distance from the source, just google "inverse square law."

You can take these light measurements for yourself (like I did) using a cheapy $95 luxmeter or you can do a much better job using a $350 Apogee PAR meter, since PAR is what we're really interested in. Or you can just forget about all that and remember that the center of the tank has the strongest light and the edges have the dimmest light. Also, the light is much stronger 8" beneath the surface than it is on the sand bed.

So exactly how much light are we talking about here when we say that SPS corals require a lot of light?

All of the scientific literature uses Micro Einsteins per Meter Squared per Second (or Micro Mols per Meter Squared per Second) instead of the typical PPFD units to measure PAR that are common in the hobby literature. So I have to stick with what's in the literature for the time being.

When the sun is directly overheat on a clear cloudless day in the tropics the intensity of sunlight at the water's surface is approximately 2,000 micro mols per meter squared per second. One meter beneath the surface the intensity will have dropped to 1,600 micro mols per meter squared per second. At five meters depth it is around 950 and at 10 meters depth it has dropped to 600. If you want to measure it at 20 meters depth you will get around 300 micro mols per meter squared per second.

Most of the corals we keep in our reef aquariums are collected at around five meters depth. Many of the SPS are collected at only one to three meters depth and some corals may be collected at ten meters depth. In general, they like to collect corals that are easy to get to because they don't like working too hard.

So, does that mean I have to provide the same intensity as natural sunlight? No, not at all, even for SPS like Acropora. For starters, it's not always a clear, cloudless day in the tropics. And those numbers above were all taken at noon, not an hour after sunrise or an hour before sunset.

Exactly how much light do I need to provide for SPS like Acropora, which is known to require the most light?

For Acropora formosa and A. gemifera, you will need to provide substantially more than 170 micro mols per meter squared per second because that's their compensation point. Their saturation point is 340 micro mols per meter squared per second. If you can give them 250 micro mols per meter squared per second you should be good to go. For the sake of comparison, Montipora tuberculosa has a saturation point of 180 micro mols per meter squared per second and Pocillopora damicornis has a saturation point of 225 and Pavona varians has a saturation point of only 110. I couldn't find their compensation points.

None of that is really all that important for you at this point. Just remember that, in general, SPS require more light than LPS and LPS require more light than most softies. Tridacna crocea clams require as much light as Acropora corals and T. maxima clams require slightly less light than crocea clams. Those two species of clams belong on the rock structure, not the sand bed, for several reasons. Some people like to stick them on the sand bed just so they can view them easier. The other Tridacna clams all belong on the sand bed.

More than you asked for, I know. I got a little carried away.

P.S. -- I forgot to stick in some of the photoinhibition points. The photoinhibition point for most Acropora corals is around 600 micro mols per meter squared per second. So right away you can see that their photoinhibition point may easily be exceeded in the middle of a cloudless day in shallow water. Yes, that happens. And those corals have adapted so that their photosynthesis process does shut down during certain parts of the day on a clear day when photoinhibition has been reached. Many Acropora have even adapted to occasional exposure to the air at extreme low tide and they survive by exuding a lot of slime coating to protect them from direct sunlight. Too much exposure will cause them to bleach and die. High water temperature for extended periods of time will also cause them to bleach.

A few more: The saturation point for Montipora capitata is only 135 micro mols per meter squared per second and its photoinhibition point is only 250. The photoinhibition point for Pavona varians is 350. For Porites lutea, saturation point is 400 and photoinhibition point is 750. Wow!

It's hard to find the ones you really want to know about online. I couldn't find Montipora capricornis but I would guess that its saturation point is around 175-185.

[Parrothead]

Here's another thought, if you are going diy, check out the Icecap 660, it will power 4 bulbs up to 4' ea, get 2 as your opt. 2 says, and you can stagger the bulbs to cover the whole tank and have 8 4' bulbs over your tank giving you more than adequate lighting for anything you would want to keep. Just a thought