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Discussion Starter · #1 ·
I've got an oddly shaped 20g tank.

It measures 11 3/4" x 32" x 13". The 13" measure is the distance from the water level to top of the substrate. Based on my calculations the water content of the tank(including rocks and decors)is roughly 20 gals or less.

If I put a 34(combined output of several bulbs) watt fluorescent bulb about 2-3 inches above the water level will it be considered medium lighting?
 

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Fluorescent bulbs can be T12, T8, T5NO, T5HO, or CFL (screw-in), and each of those will give a different light intensity for the same wattage. With the CFL bulbs the intensity also varies greatly with the orientation of the bulbs - vertical or horizontal above the tank. And, for all of them the intensity can vary by at least 2 to 1 with the quality or presence of a reflector. That makes it pretty hard to answer your question.
 

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Discussion Starter · #4 · (Edited)
Sorry about not giving more details.

I already have 2 8watt T5 normal output bulbs in hand. Since I will be turning this tank into a planted one I obviously need more lighting. Adding more T5s are too expensive for me so I will go with screw-in CFLs. I will add 2 9watt CFLs mounted horizontally.

Here is a very rough sketch on how it will be placed inside my hood:
 

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The CFL bulbs, if you have good \_/ shaped reflectors behind them should give you about 15 micromols of PAR. The T5NO bulbs might give you another 15 micromols of PAR, so you could have around 30 micromols of PAR, which would be low-medium light. If all of the bulbs are kept close together, and not spread out as your sketch shows, you could get as much as twice that PAR, or medium light, but it wouldn't be very uniform over the whole substrate. This is all just a rough guess.
 

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The CFL bulbs, if you have good \_/ shaped reflectors behind them should give you about 15 micromols of PAR. The T5NO bulbs might give you another 15 micromols of PAR, so you could have around 30 micromols of PAR, which would be low-medium light. If all of the bulbs are kept close together, and not spread out as your sketch shows, you could get as much as twice that PAR, or medium light, but it wouldn't be very uniform over the whole substrate. This is all just a rough guess.
well he is talking about over a 20 long, so I would guess the t-5 would not be more than about 4 inches apart. That would leave about 10 inches on either end not covered by light, so center each CFL over the remaining 10 by 12 square at either end. That would put the cfls about 5 inches from the ends of the t-5s.

I highly recommend clip style worklights sold at Lowes. They have ones with metal reflectors and you can choose from 5", 10" and 13" diameter reflectors. I thought they use to have 8" ones but I don't see them online. You can see pics of the 5" ones in my 40 gallon thread.

I'm not sure which diameter reflector would be best in you case...10" maybe.
 

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well he is talking about over a 20 long, so I would guess the t-5 would not be more than about 4 inches apart. That would leave about 10 inches on either end not covered by light, so center each CFL over the remaining 10 by 12 square at either end. That would put the cfls about 5 inches from the ends of the t-5s.
You are right. I missed that the T5s are much shorter than the tank length. In that case it is much more likely that it will give only low light, possibly too low.
I highly recommend clip style worklights sold at Lowes. They have ones with metal reflectors and you can choose from 5", 10" and 13" diameter reflectors. I thought they use to have 8" ones but I don't see them online. You can see pics of the 5" ones in my 40 gallon thread.

I'm not sure which diameter reflector would be best in you case...10" maybe.
An aquarium lighted with those worklights can easily be changed from low to medium to high light just by using higher wattage CFL bulbs. I found that to be a very good way to light 10-20 gallon tanks.,
 

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You are right. I missed that the T5s are much shorter than the tank length. In that case it is much more likely that it will give only low light, possibly too low.

An aquarium lighted with those worklights can easily be changed from low to medium to high light just by using higher wattage CFL bulbs. I found that to be a very good way to light 10-20 gallon tanks.,
yup! and you can increase or decrease the number of light easily as well...that's what I like so much about using them, versatility!
 

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Discussion Starter · #9 ·
Does this mean that with my tank dimensions and my lighting setup and arrangement(2 8W T5NO and 2 9W CFL) I will be getting low light? I dont want to center all the bulbs because i do not want a bright area in the middle and dark spots near the sides.

Edit: the image above is very inaccurate. It is just to give you guys an idea on the arrangement of the bulbs. I cannot find any reflectors here in my place(I'm not from the states or UK) but I can change the CFLs to 11 watts. How will it do?
 
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