I've got a reservoir like that! The air pump/stone is a good thing! It produces oxygen for your plants roots to absorb!Do you have your reservoir,in the light? Or the dark! Is it a clear bucket,or what? Algae will build up in the bucket if exposed to light.It could be that.The airstone is just stirring it up! Do you have the pump on a timer?I would run the airstone 24/7.Put them on a drip system.1 emitter per pot.It has a setting on the emitter,for 1/2 or a gal/hr.

Ga Grown