How much light is required??????

[The Grizz]

I was hoping some one could tell me how much light is required for a tank with a depth of 18" . I am planning a canopy above the tank about 6 - 8 " so I can get into it easily. Need some idea of what to do. I think it is to shallow for 250 MH, could I go with all T5's and if so how many 54W T5's would I need.

If you have seen my 155 Bow Front build and coral pic then you have an idea of what I have for coral and lighting in there. The new tank is going to replace this one and I would like to use as much of the lighting that is in the 155 on the new tank ( 96" x 22" x 18") but I think the MH will be to much. Please let me know what you have on your tank if it is shallow or if you are a lighting guru tell me what I need.

Thanks to all in advance.

[24storm]

My frag tank is 12" deep 48" long and 24" front to back i have 2 250 watts over it will no problems i keep the lights about 12" to 14" off the water i have SPS and LPS in it.

Keith

[fencer]

8 t5 ho's would do it...well at least in a std 72 gallon....lights up every corner of the tank. I tried that last summer but went back to MH's/t5's

[Delphinus]

If it helps, I don't think there's such a thing as "too much light" but the caveat is that there is such a thing as "too much light too fast." If something is coming from a darker tank it could suffer light shock if not properly acclimated to the higher intensities, but usually things will adapt and be fine. I had 2x250W supp'd with 2x110W over my 18" tall 75g for 7 years before I shut that tank down last year, the halides were maybe 4" over the surface.

The nice thing about an 18" tank is that it's not terribly deep so it's a bit of good fortune in that you can pick pretty much any lights you want (t5, halides, etc.) and I think it would be hard to go wrong with any of them.

[The Grizz]

I would like to use the lighting I have in my 155 for this one as the MH Ballasts are brand new Ice Caps and the bulb's are same age as the ballast. The T5 I have in there are all 48" 54w so they will span the whole tank as they are overlapped in the 155 by 12" now. I just don't want to have a wipe out because I have to much light, if that is possible.

[the marine apprentice]

hey greg, id imagine if you just have them halides a bit higher then ya have them right now you will be fine untill everything gets acclimated to the light then if you wanted you could lower them a bit more. my 250 is sittin 16inchs above the water surface in my tank and my tank is 15inchs deep. and my clam is happy as can be

[The Grizz]

I was hoping to have the light's lower so that the canopy doesn't ahve to be so big. May be a shorter time sysle on the MH and a 4th set of T5 woul dbe a way to go.

[The Grizz]

any more opinions or options out there??

[Delphinus]

Keep the lights you have now. That sounds like a killer setup. It also opens the door for more light loving things down the road if that floats your fancy. :)

If you are concerned about light shock for the first week or two, here are two methods that work well for acclimating critters to higher light (well, ok, 3, but let's ignore the first one since I think it won't be an option):

1) If the lights are suspended over the tank, adjust the height upwards and slowly lower them over time.

2) Layers of eggcrate. At least one layer, or two if the need is extreme. Remove the eggcrate layers a couple days at a time.

3) (My personal favourite, done this a few times and it's worked out well). Let's say your photoperiod is from 10am to 10pm. Keep the photoperiod 10 to 10, but adjust the lights so that they're on for 15 minutes, off for 45 minutes. After 4-5 days adjust it so it's 30 minutes on, 30 minutes off. Another 4-5 days 45 minutes on, 15 minutes off, last but not least, on all the time. Takes about 2 weeks but then you're generally set after that. Plus all this time you're looking at your fish/corals/etc and will have a sense of how it's going - so you can slow it down if need be, or speed it up even if you think it's going fine.

[globaldesigns]

I would keep the lights you have, Tony has some great points.

[Ian]

I have a 90 gallon that is 18 inch high with a tek 8 bulb fixture over it and I have no issues with light...8 bulbs in fact are a bit wide as the outside ones spill a fair bit of light outside the tank.

[The Grizz]

My light run in a sequence.

9 am Actinic's on / 9 pm off
10 am Fiji Purple on / 8 pm off
11 am 10,000k's on / 7 pm off
1 pm MH on / 6 pm off
Moon light on at 9 pm / off at 6 am

Tony your 3rd technique sounds easy enough. I will have to find different timer's though.

[fishytime]

Greg....my tank is 20" deep and Im running 6 bulbs per side(12 total), light 5-6" off the water...

[The Grizz]

Greg....my tank is 20" deep and Im running 6 bulbs per side(12 total), light 5-6" off the water...
Are they all T5's? What are the bulbs? Wattage? Actinics/fiji/k rating. Hope you get what I am trying to say