The jet aeration system from Mass Transfer Systems has a nozzle designed to transfer oxygen without using a blower. In low-oxygen-demand cases, the aspirating system is cost-competitive with blower systems in depths up to 14 feet. Consider that in addition to the blower cost, there are installation, switchgear, cabling, operating and maintenance costs. At liquid depths below 10 feet, the horsepower demand is similar for both blower and aspirating systems. With increasing depth, the blower system will have a horsepower advantage. Using a variable-speed pump can swing the aspirating horsepower lower, particularly in situations where oxygen is not continuously needed. Variable speed also extends the range of oxygen transfer considerably. When air is not required, the system is effective for mixing only. Future requirements for more air can be met by simply connecting a blower to the air pipe. 508/404-1025; www.mtsjets.com.