It is possible to convert the AS200 into an AS280 by adding an additional filter housing and cartridge. This is a simple process and one done by many of our customers in the past. The cost of this depending upon the filters you already have in the AS200 unit. If you have the AS001K9/10 filter then it is only a matter of adding a fluoride removal filter AS001A9/10 and a filter housing. Please contact Aqua Safe for the latest cost of doing this.