"AIR AGITATION"
Most metal finishing process baths benefit from agitation of the solution -- it keeps fresh plating solution in contact with the parts, keeps the solution well mixed for homogeneity and constant temperature, and helps to dislodge hydrogen gas bubbles which may form on parts that are being electroplated (from electricity hydrolyzing water into hydrogen and oxygen gas).
The most popular agitation method in plating and anodizing is 'air agitation': pipes with holes drilled every few inches are laid along the bottom of the tank, often held down by plastisol coated weights, and air from a low pressure blower is pumped into them. The air exits through the holes, then races towards the surface, agitating the solution.
Shop air is low volume and high pressure and oily, and usually considered inappropriate for the task. Low pressure regenerative blowers are relatively inexpensive, provide plenty of volume, and are generally well suited for air agitation.
