You need to give more details. What size tank is it?? Do a google search on PAR (photosynthetically active radiation) once you understand, youll be better placed when looking at the tech specs on manufacturers LED fixtures. There is also a rule of watts per gallon, with 2-3 watts per gallon giving you the light your after. This is a rule that is outdated when looking at LEDs as they generally run at low wattage levels. Do some research on PAR