volts? im assuming you mean watts. the wattage dictates the "power" of a light fixture, not the voltage. in that cause, the most common would have to be the 120w dimmable led
fixtures. you really shouldnt need any more power than that and youd need 2 for that tank. there are lower-wattage versions, but unless you find a steal of a deal, the price difference between the 120w and lower wattage isnt worth the sacrifice in power output.