Metal Halide question 70W vs 175W vs 250W

[silveroak]

All,

Since I am getting ready to set up my first saltwater tank, I have been doing a TON of reading, and have a question about metal halides. I assumed that the wattage required had more to do with the depth of the tank for penetration. Is this not the case? For instance, I am looking at people that have a frag tank, and are using 250W halides over a tank that is 8" deep. How do you determine what the proper halide to get actually is?

edit: also, I read that MH is good to basically light a 2' cube of water. I can see this with a 250W or bigger, but surely a 70W with a good reflector could do 2'x2'x6-8" right?

Thanks!

 

[DaveG99]

I have a 40 breeder and a single end 175watt with a spider type reflector lights up the whole 36"x18" tank.

 

[Bayou]

@silveroak wrote:

The proper wattage of lamp to get depends on many, many factors. What size is your tank going to be? What kind of corals do you plan on keeping? How fast do you want them to grow? How much money do you want to spend? Will you have an enclosed canopy that will retain heat? Do you have anywhere to put the ballast(s)? Do you want an all-in-one fixture or a DIY or independent lamps/reflectors? Have you considered what reflector you want? Reflector choice is very important.

Once you decide on a wattage you can start considering color. Do you want a "white" tank(10k) or a "blue" tank(20k)? Or something in between (12-15k)? Will you suppliment the MH with some kind of floresent actinic bulb? Do you want your corals to glow (lots of blue spectrum)in the tank? Or do you want a more natural look?

If you list some specifics lots of people will chime in with ideas and recomendations. Good luck to you!

 

[silveroak]

@Bayou wrote:

The proper wattage of lamp to get depends on many, many factors. What size is your tank going to be? What kind of corals do you plan on keeping? How fast do you want them to grow? How much money do you want to spend? Will you have an enclosed canopy that will retain heat? Do you have anywhere to put the ballast(s)? Do you want an all-in-one fixture or a DIY or independent lamps/reflectors? Have you considered what reflector you want? Reflector choice is very important.

Once you decide on a wattage you can start considering color. Do you want a "white" tank(10k) or a "blue" tank(20k)? Or something in between (12-15k)? Will you suppliment the MH with some kind of floresent actinic bulb? Do you want your corals to glow (lots of blue spectrum)in the tank? Or do you want a more natural look?

If you list some specifics lots of people will chime in with ideas and recomendations. Good luck to you!"]

Thanks for responding! I wasn't sure why I wasn't getting a good response on this question, but it looks like I didn't really ask it very well. There is another thread that I created asking if my proposed lighting was overkill for my display, but I started thinking (in the spirit of not being limited as to what I could do) about what if I wanted to add a very shallow frag tank that would be plumbed into my main display. The display tank is 100 Gallons and built into a huge shelving unit that covers the entire width of my office. Really beautiful, but limiting as to what I can do. On the display I am looking at a hanging fixture that is 48" with 2x250W 15K HQI and 4x54W T5 for actinic supplementation. This fixture also has cooling fans and remote ballasts for the MHs. I am adding an intake and exaust fan into the unit to add airflow across the top of the tank and provide some evaporative cooling. The remote ballasts will be placed on the top of the shelves next to the tank but about 8 feet up, hidden from view by the HUGE mouldings on the unit.

So I was thinking that if I wanted to (ever) add a frag tank to my system it would have to be 24x24 and only about 6 inches deep. Knowing that a MH is good for about a 2 foot cube at 250 watts, I was really wondering why so many of the people that set up these really shallow tanks are putting 175 or 250 watt systems over 6 inches of water. It seems like it would be the most cost effective to put a 70W MH over the setup with a 6500-10K bulb for maximum frag growth, and then put them in a display tank with actinic and a bluer MH bulb to color up. I would likely DIY the MH unit but use a decent brand name reflector (probably the Lumenbright DE reflector). I also realize that the size that you would want to grow frags to, or cut would determine the depth of the tank that you would need, but If you are cutting 1" frags of SPS, you could get some serious growth in that extra 5" of water before you would have to move them.

The 6" depth was the example for my purposes, but what I am really looking for is an explanation of what sizing to use for whatever the application and to determine what tank volume would require what lighting.

If I can get that put together I will also get an idea of the lighting I want to get for my QT tank (since again, I dont want to be limited, and will be QTing all my corals as well as livestock)

I'm really trying to get a handle on all of this, and I appreciate anyone that takes the time to help me learn.

 

[Bayou]

Your not scared to jump right in are you! LOL
Let me see if I can give my opinion on a few points:

@silveroak wrote:

That sounds awesome.

@silveroak wrote:

That will be more than enough light to keep anything you want. Hiding the ballasts is a good trick.

@silveroak wrote:

Intake and exhaust fans inside a canopy should be considered mandatory. If open air, they can be optional.
Evaporative cooling fans should be pluged into a controller so that you can adjust when they come on. (You will not need them in winter)

@silveroak wrote:

Frag tanks should be at least 8" to 1'. 6" w/ a 250W Halide blasting over it will increase the water temp way too much. The temp swing will prohibit growth of the corals and probably kill them. Also - A MH is good for a 2x2 footprint at any wattage. 250 W will penetrate into deeper water, but the light output will cover the same footprint at any wattage - 75, 150, 175, 250, ext.

@silveroak wrote:

If you are going to grow frags under a 6500k bulb, then move them into your display you might as well just grow them in your display. And honestly you don't want a lot of brown corals in your desplay waiting to color up. The added growth of a 6500W bulb over a 12k bulb is minimal. Good water quality and feeding the corals will account for more growth than a 6500w bulb. I'm basicilly saying they are more trouble than they are worth.

@silveroak wrote:

Think deeper water, more wattage.

@silveroak wrote:

Go cheap on QT lighting. Your corals will not be there long.

While you are planning things - plan on a convient topoff water storage container. Do you plan to have a sump and/or fuge? Is there a convient way to do water changes?

Good luck

 

[silveroak]

@Bayou wrote:

You betcha i'm planning on having a sump to keep as much equipment out of my display as possible. The sump will be relatively small, as It has to fit in one side of a cabinet with an available footprint of 30x24. The other side will house the ATO reservoir and all of the external equipment that doesn't work in the sump. I am still owrking on planning out how I will do the water changes, as I will have to mix and bring in the water from somewhere else in the house. My wife is 100% on board with the tank, but she would freak if I had a mixing barrel in my office I think.

I am also planning on trying to be as green as possible in this adventure, and will have a storage container in the garage for used saltwater that is changed out (for normal changes) to be recycled for use in growing phyto for the corals or hatching BBS. don't think that I will have to keep it all, but even if I recycle 10% of my used water it will be better than having it go down the drain right? overall it shouldn't be too much of an effort to keep it aerated for use.

 

[silveroak]

By the way, here is the cabinet and everything for reference:

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This is a view from the dining room into my office to give some perspective as to how narrow the room is:

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please ignore the goofy looking dude that walked through the picture. (My wife gets mad at me for not paying attention when shes taking pictures)

And here is the desk on the other side of the room. That window that you see covers that whole wall from the cabinets to the desk. Its huge, and there is great light in that room.

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[Bayou]

That will be an awesome tank. You should do a build thread. You will get plenty of opinions there! LOL

 

[the floor guy]

whats behind the tank? can u access it from behind?

 

[silveroak]

@the floor guy wrote:

Not exactly sure what you are asking, so I will give a complete response and hope it covers it.

That unit is built all the way back, and rests against the wall. Its an interior wall that backs up to the master bathroom on the other side. This is great in my opinion, as it gives me quick access to a water source, and a drain. I do however doubt that my wife would be as thrilled about it as I am, so I have decided that if I am going to use any of that I will have to have her come home to a hole in the bathroom wall, and just beg forgiveness.

I can't access the tank from the back directly, but the opening in there is 24" deep, and the tank is only 18. that leaves me a little room to play back there. there is also a pretty good amount of room over the tank if I remove the lights to climb up there.The plan (my plan, not the wife's) is to eventually upgrade the tank to a reef ready that is 60" wide by 24" deep, and redo the center part of the cabinet when I do that upgrade. The space in there would fit that tank now, but there is some MAJOR trim removal that would have to happen to get the tank in. I also have 6" on each side of the tank to play with if I add vortechs or anyhting that requires magnets.That project is a few years off though.

Hope that answers your question