# New to forum and light questions



## Hoppy (Dec 24, 2005)

A 20L tank is only about 13 inches high, so if a light sits on top of the tank, and you have 2 inches of substrate, the light is only 11 inches from the substrate. A Coralife (Aqueon) 2 bulb T5NO light will give you about 40 PAR, which is about the most light you can use without using CO2, and would be low medium light. An ordinary one bulb T8 light in a typical aquarium light hood with just white plastic acting as a reflector should give about the same light intensity. To go lower you would need to raise the light higher above the tank.


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## skaerber (Apr 10, 2013)

Thank you, I honestly had no idea about how depth would effect how light intensity the only guidelines that I ever found that were 'concrete' were the watts/gallon. Any way just clarify: A standard hood with one full spectrum t8 bulb is sufficient for low to med light plants in a 20L, without co2; correct? With that I can budget with more certainty, again thank you. 

I have one more question, unrelated to lighting: I plan on having a few corydoras catfish, but need to know if fluorite is safe as a substrate for them as it seems to have sharper edges than most substrate. Anyone able to enlighten me?


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## Wannaberooted (Jun 24, 2012)

Flourite is fine for Corys.


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## Hoppy (Dec 24, 2005)

skaerber said:


> Thank you, I honestly had no idea about how depth would effect how light intensity the only guidelines that I ever found that were 'concrete' were the watts/gallon. Any way just clarify: A standard hood with one full spectrum t8 bulb is sufficient for low to med light plants in a 20L, without co2; correct? With that I can budget with more certainty, again thank you.
> 
> I have one more question, unrelated to lighting: I plan on having a few corydoras catfish, but need to know if fluorite is safe as a substrate for them as it seems to have sharper edges than most substrate. Anyone able to enlighten me?


Yes, a standard hood, with one T8 bulb is sufficient for a 20L tank. It can be a 6500K bulb, a cool white bulb, or a more expensive "full spectrum" bulb. With that light on that tank, and with CO2, you could grow just about any plants you want. However, plants that can have reddish leaves may need more light to get the best color.


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## petersmith98 (Nov 19, 2020)

Although I don't know much about stacking tanks, I wish you success


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