I was spending $5 or more a week on water, between the once a week water change and topping off. I picked up a coralife 50gpd (gallon per day) 3 stage unit for $150.00. It takes forever to get the final product, seems to be 15 gallons or so of bad water to get 1 gallon, but will save me money in no time. Plus, no more running to the store for water.