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Discussion Starter · #1 ·
i assume im at medium light is that correct?

hagen GLO t5HO 78watt
40 gallon tank
flourish excel
nitrogen
potassium
comprehensive
dry ferts on the way when this runs out but will continue excel dosing

i dont understand the difference of the watts per gallon rule when applied to t5 bullbs



 

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A 16 inch deep tank, with two T5HO bulbs, with individual highly polished aluminum reflectors, sitting at the top of the tank, unless those bulbs are around 10 inches or more apart, has high light intensity. You would have to raise the fixture about 8 inches above the tank to get back to medium intensity. If you raise the fixture you also get much more uniform lighting intensity all over the tank.
 

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Fresh Fish Freak
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The Glo fixtures don't have individual reflectors, Hoppy. Both bulbs are housed side by side inside a round half-circle reflector. But the reflector could be a mirror it's so highly polished.

I've wondered if this shape of reflector would increase or decrease the PAR output in the tank?
 

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A 16 inch deep tank,
My 46g is 20" deep, and I believe a standard 40g also is 20" deep, although you may be taking into account substrate depth, which gets you closer to 16".

... with two T5HO bulbs, with individual highly polished aluminum reflectors, sitting at the top of the tank, unless those bulbs are around 10 inches or more apart, has high light intensity.
How does moving them farther apart reduce intensity?

You would have to raise the fixture about 8 inches above the tank to get back to medium intensity. If you raise the fixture you also get much more uniform lighting intensity all over the tank.
I've got mine raised about 3-4", partly to reduce intensity, but mostly for the more uniform lighting. Otherwise the tall plants in back get very little light near the top. If I move the light towards the back to help them, then there are too many shadows in the tank, which doesn't look good.
 

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Fresh Fish Freak
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Spacing the bulbs helps distribute light more evenly across the width of a tank. Also, individual reflectors (wrapped one per bulb help ensure that the light from each bulb is directed down into the tank, instead of light being directed at each other when bulbs are side by side.
 

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Discussion Starter · #9 ·
i have fish that love to jump. i do have the light holders that hook on to the side of aquarium but i have a glass canopy so they dont work. is there a decent way that any of you have found to raise a light but keep the tank covered, without suspending from ceiling.

i was thinking some kind of screen with largish holes to prevent shade?
good idea or no?
 

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The Glo fixtures don't have individual reflectors, Hoppy. Both bulbs are housed side by side inside a round half-circle reflector. But the reflector could be a mirror it's so highly polished.

I've wondered if this shape of reflector would increase or decrease the PAR output in the tank?
I'm not real sure, but I suspect that the Glo fixture would give lower intensity than fixtures with individual reflectors. That might reduce the intensity to the upper medium light area.

If two bulbs are separated by several inches one bulb is further from the maximum intensity area of the other bulb, so the two bulbs won't double the intensity, just increase it somewhere around 50-80%, depending on how far apart they are - one would be 16 inches away and the other might be 18.5 inches away (if the bulbs are separated about 8 inches). So, the farther away bulb would give (16/18.5)^2 as much intensity - 75% as much as the closer bulb.
 

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Fresh Fish Freak
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i have fish that love to jump. i do have the light holders that hook on to the side of aquarium but i have a glass canopy so they dont work. is there a decent way that any of you have found to raise a light but keep the tank covered, without suspending from ceiling.

i was thinking some kind of screen with largish holes to prevent shade?
good idea or no?
You could build a rod system to suspend your light from, like Tom Barr did for this tank: http://www.plantedtank.net/forums/tank-journals-photo-album/59705-toms-180-wood-scaping.html

And you could use eggcrate cut to fit the top of the tank instead of a glass canopy, but I'd just stick with the canopy, personally.
 

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Discussion Starter · #12 ·

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You could build a rod system to suspend your light from, like Tom Barr did for this tank: http://www.plantedtank.net/forums/tank-journals-photo-album/59705-toms-180-wood-scaping.html

And you could use eggcrate cut to fit the top of the tank instead of a glass canopy, but I'd just stick with the canopy, personally.
hey Laura, is there any other option (e.g. netting) that can be used?! I dont like my glass top either... they get water condensation and also gets dirty. I finally took the tops off while changin water today, n realized I'm getting @least 15-20% more lights coming through now! thnx.
 

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Well, anything is going to obstruct light at least some.

I wouldn't use netting b/c of the risk of fish getting stuck in it. Screen (like outdoor or window screening) on a custom-built frame would probably work, but also block a lot of light.

You might try and find a large rigid plastic mesh other than eggcrate, but those are also going to block light considerably. Metal would rust...
 

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was thinkin 1/4" (or 5/16" pond) netting. My fishes are either smaller or larger then that. and dont think Neons jump, just the Gouramis' im worried abot. so should be fine. & think that size netting will block less light them eggcrate (where u get that anyway?), right?? :D
 

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You don't have any catfish? Cories/Otos/Plecos could really easily get their rigid fins tangled in netting, especially when they make their dashes to the surface for air.

You can find Eggcrate at the Big Box stores like HD & Lowes, usually over in the lighting section.
 

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Discussion Starter · #17 ·
You don't have any catfish? Cories/Otos/Plecos could really easily get their rigid fins tangled in netting, especially when they make their dashes to the surface for air.

You can find Eggcrate at the Big Box stores like HD & Lowes, usually over in the lighting section.
i totally agree i have 2 bulldog-rubbernose plecs and they will hit the canopy from time to time along with my butterfly and golden wonder killies

i like theidea of the egg crate but have to see it first. dont need wounded fish.
 

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my 55 gallon link on my sig has list of fish... do have few Ottos, & 2 yo yo loach. n yes, they do run around crazy (ALL DAY!). but never seen them dashing for the top. just all around the tank & sometimes wall to wall (when they freak out)... lol
 
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