Wattage of lights for a 20inch deep

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Hi,

Can anyone let me know the light wattage requirement for a 20 inch deep aquarium (T5 or T8 as well)

Size of the aquarium is : 120cm (l) x 37cm (w) x 50cm (h)

[bs6749]

Wattage is only a measure of the power used to run the lights. You should be more interested in the lumens (intensity of the lamps) and temperature rating/spectrum of the bulbs.

Looks like your tank is roughly 57gal and since it is almost 20" deep I'd go with a T5 fixture as it has better penetrating power than the T8's would. They are also more efficient and you could get away with a 48" strip light or two. Look for around 100W total on a T5 fixture or two fixutes over that tank to give you high lighting. A T5 lamp is about 1.75 times as effecient as a NO bulb (normal output bulb), on which the watts per gallon rule was based. You'd need roughly 175W on a NO fixture to produce an equivalent amount of lumens as compared to the more efficient T5's.

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Thanks a lot mate.. I will go for 2 50W T5 as suggested.But does the coloured lights in these items effect the plant growth in anyways..lets say for instance, will 2 50W blue marine lights penetrate more than 2 50W Green/Red light?

[bs6749]

I believe you are referring to the temperature of the bulb in kelvin. The temperature/spectrum that is ideal for plant growth is 5,000-10,000K, and 6,700K is one of the better bulbs for plants to grow as it has the right peaks in the spectrum. I think you are referring to actinic bulbs when you say "blue marine lights" and those are not beneficial at all to plants. The most common bulbs you will see will be rated at 6,700K or 10,000K and either of those are good for plants. I believe that blue penetrates the deepest as it is on the longer side of the wavelengths in the visible spectrum, but it is outside of the useable range of plants so you should avoid it for that reason.

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thanks a lot for the guidance.. :)