lighting suggestion 32g

kevinicus

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Aug 18, 2008
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Well,

I have a 32G but I'm really confused with what lighting. What do you guys think about having 70W mh suspended 30cm above the water?

The tank will be CO2 enriched, EI dosed and intend to grow such plants as Pogo and HC

I don't need so much light that the growth rate is extreme but would like a suggestion to how much light I would require for a stable lush tank.

thank you in advance,
Kevin
 

VaughnH

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The amount of light needed depends mostly on the height of the tank, and the length of the tank. I'm not sure of the dimensions of a 32 gallon tank, so I have no idea what lights would work best on that one.

The light intensity drops with the square of the distance from the bulb, so the height is the single most important determinant of the amount of light needed. And, to get good coverage of the entire substrate, the light bulb needs to be about the same length as the tank length. But, the front to back depth of the tank has little effect on the amount of light needed - two tanks with different depths, but the same height and length get very nearly the same light intensity at the substrate with the same bulb.

When you use a single MH/HQI light fixture it cannot give nearly uniform intensity over the entire substrate except for tanks with length and depth about the same, or unless the fixture is raised so much that most of the light spills out into the room.
 

kevinicus

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Aug 18, 2008
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VaughnH;34529 said:
The amount of light needed depends mostly on the height of the tank, and the length of the tank. I'm not sure of the dimensions of a 32 gallon tank, so I have no idea what lights would work best on that one.

The light intensity drops with the square of the distance from the bulb, so the height is the single most important determinant of the amount of light needed. And, to get good coverage of the entire substrate, the light bulb needs to be about the same length as the tank length. But, the front to back depth of the tank has little effect on the amount of light needed - two tanks with different depths, but the same height and length get very nearly the same light intensity at the substrate with the same bulb.

When you use a single MH/HQI light fixture it cannot give nearly uniform intensity over the entire substrate except for tanks with length and depth about the same, or unless the fixture is raised so much that most of the light spills out into the room.

Thank you for your reply.

The tank dimensions are 60cm x 45xcm x 45cm
Are MH's recommended for this tank given its height?
In a MH direction, how does 150W and raise them up higher for more uniform spread?
 

VaughnH

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I think that MH light would work fine for that tank. The ends of the tank will have a little lower intensity perhaps, but not by much. Did you see the pictures of Tom's bent electrical conduit version of the ADA light hanger? Just be sure to allow room to raise it at least a foot, if necessary.
 

aquabillpers

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Is there an alternative to MH lighting for a fairly deep tank?

I have a 29 gallon, non-co2 tank that is 15 inches deep and has Coralife 65 watt broad spectrum lighting. That is far too much light at the top and middle of the tank, but not enough at the bottom. The rooted plants there do grow, but in searching for light they get too tall. I have 6 inch tall E. tenellus and 10 inch tall C. wenditii, much higher than they are supposed to get and too tall for the foreground in which they are planted. Both will probably grow to the top of the tank.

There is also excessive algae on the glass that requires weekly cleaning.

Any ideas?

Bill
 

kevinicus

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Aug 18, 2008
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VaughnH;34535 said:
I think that MH light would work fine for that tank. The ends of the tank will have a little lower intensity perhaps, but not by much. Did you see the pictures of Tom's bent electrical conduit version of the ADA light hanger? Just be sure to allow room to raise it at least a foot, if necessary.

thanks, I'll give the 150W MH at 30cm a shot. I really don't mind the light splash so i can raise it higher to reduce light if required... if only I could find somewhere to borrow a PAR meter it would help in adjusting the height of the MH with my tank
 

VaughnH

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Jan 24, 2005
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aquabillpers;34537 said:
Is there an alternative to MH lighting for a fairly deep tank?

I have a 29 gallon, non-co2 tank that is 15 inches deep and has Coralife 65 watt broad spectrum lighting. That is far too much light at the top and middle of the tank, but not enough at the bottom. The rooted plants there do grow, but in searching for light they get too tall. I have 6 inch tall E. tenellus and 10 inch tall C. wenditii, much higher than they are supposed to get and too tall for the foreground in which they are planted. Both will probably grow to the top of the tank.

There is also excessive algae on the glass that requires weekly cleaning.
Any ideas?
Bill

This has been an issue with me too. For awhile it is fun to watch plant grow up to the light, growing faster and faster as they get closer to the light. But, that fun soon stops for me. Since light intensity drops with the square of distance from the light, there can be no way to avoid this without raising the light high enough to make the increase in intensity at the top of the tank be less. That seems to dictate using a MH type light, with a reflector that prevents too much spilling of the light into the room. Or, a T5 light, with a custom reflector to keep the spillage down. Some day when my ship comes in, I may try something like that.