How many bulb watts would a 20 gallon freshwater tank use

[Turok]

Title says it all

 

[mohican]

Depends on what's in it! Just a forewarning, wpg is an old guide and u may get many different answers. I would say a 1:1 ratio is a safe, easy guide, imo.

 

[Chiroptera]

Depends! 20-30 watts is fine, by theory, unless you have plants. Some plants are recommended for a 3 watts per gallon, some even up to 5! It's easier to take care of your tank, if you have no plants, to do a 1:1. And while it's true that the watts per gallon rule is old, it's a great place to start if you don't know much about lighting.

 

[Hobgob]

Plants are great for your aquarium. They act as a nitrate sponge using it as food. Also a lot of fish like to nibble on plants for a balanced diet.

The light you want all depends on the plants you are growing. Lots of crypts will do well in low light situations. While dwarf grass for example needs tons of light...