I use an ebb/flow garden with a 25 gallon reservoir. My first two flushes I had not installed an air stone yet. When I emptied the res, the water was colored stronger towards the bottom of the tank, and the surface was coated in a darker "sludge."

After adding the air stone, the solution stayed consistent in coloration with no build up on the walls. The plants seemed much happier! Cheap improvement with great results.