What's your bioload?  I've had a 12 gallon nano with one clown, plenty of coral, one cleaner shrimp,  and a very large anemone in mine for almost 4 years.  I've done maybe 3 water changes in all of that time.  I make my own ice cubes with a very nice assortment of goodies for my tank and I feed one ice cube a day.  I also feed my anemone about 1/2 a silverside 2 times a week.  Everyone is fat and sassy, growing very nicely and all I do is add r/o water.  I top the tank off every day so my salinity stays in check.  I haven't had any kind of algae outbreak in over 2 years.  I clean my glass maybe once a month.  My growth is spectacular.  Cut back your bioload and you can probably drastically cut back your water changes.