Keep your nutrient solution fully oxygenated with an airstone. This circular 4″ version is great for the bottom of small reservoirs.
The Hailea 4″ (100mm) Flat Circular Airstone is a 4 inch diameter “slab” of porous stone. An inlet nodule is located on the inside of the ring to allow the airstone to be connected to an air pump via a length of air line. When connected to an air pump, the air will exit the airstone through the many pores in the stone. When the airstone is submerged in water or a nutrient solution, the effect is that many small bubbles are produced and released from the surface of the stone. The bubbles create movement in the water or nutrient solution keeping it well mixed.