that really depends, as it always does with "watts per gallon"
the wattage on a heater really just tells you how far above the ambient temperature it can heat water. So that depends on where you live, the temperature of your house, yada yada yada.
You live in california and are setting up a 180g. Try a 400W heater on a controller. You don't want to boil your water when the internal thermostat breaks, so spend a few bucks extra and get a nice heater with a controller :P