The basic vessel is a six-quart plastic food container. The lid is made from 3/16 sheet acrylic. Small spacers cut from acrylic scraps are fastened to the underside of the lid using solvent-type acrylic adhesive. The motor is a low-speed 120-volt synchronous motor. Speeds from 6-10 rpm have been used with good results. The 120-volt rating allows the easy attachment of a line cord for power, rather than requiring the transformer needed with many small motors. The motor and line cord may be attached to the lid with nylon hardware (metal hardware should be avoided to prevent metal contamination of the saltwater culture medium). We mount the motor off-center to create turbulence in the vessel, promoting thorough mixing. The end of the nylon rod (Fig. 5b) can be bored for a friction-fit to the motor shaft, allowing easy removal. The polyethylene paddle can be made from a surplus cover from a rack of disposable pipette tips, and friction-fit in a slot cut in the nylon rod shaft.