The Pearling Effect

    

     Pearling is the beautiful effect of tiny oxygen bubbles forming on the leaves that occurs when the water is saturated with oxygen and additional oxygen produced by the plants simply forms a bubble and floats to the surface rather than being dissolved into the water. This occurs at different times depending on the rate of growth and oxygen levels during the night, but in general it occurs more towards the end of the light period or at least in the second half.

     When we make a water change a similar thing occurs due to the pressure the tap water is held in the pipes. This saturates it with gasses and will therefore appear to make the tank pearl temporarily.
     Not having pearling doesn't mean the CO2 isn't being utilized or that the plants aren't photosynthesizing, it just means your O2 levels have not reached a point of saturation in the water.
     If you want to make your plants start pearling:

     - you need to have a good illuminated tank, more than 0.7W/liter.

     - the tank need to be planted heavily with fast growers.
     - keep your CO2 stable at around 30ppm.
     - add fertilisers, both macro and micronutrients.