Selecting a reliable and effective diffuser for your pond aeration system
The main reason bottom aeration is beneficial – as opposed to a surface aerator or a fountain – is that it mixes the pond from the bottom up, while transferring oxygen into the water. Many industry professionals believe that the mixing is more important than the oxygen transfer itself. Mixing evens out the dissolved oxygen (DO) at all depths and prevents thermal stratification – a barrier that separates cold water at the bottom from the warmer water at the surface. Surface water naturally receives oxygen from the atmosphere and through photosynthesis of algae/ aquatic plants. If a pond has stratified, the bottom can become depleted of oxygen which prevents “muck” from decomposing and therefore can produce a smell and impact water clarity. Also, fish will not get the oxygen they need to thrive and survive when they seek refuge from the warmer surface water during the warmer months.
There are 3 main bubble size ranges for diffusers. A fine bubble diffuser produces a bubble up to 3 mm in size. A coarse diffuser has holes with a pore size from 6- 50 mm. In between is considered a medium bubble diffuser (3-6mm).
Fine Bubble Diffuser:
Advantages: Fine bubble diffusers produce many small bubbles that slowly rise to the surface. The high volume provides more surface area as compared to course bubbles, allowing for about 2x’s the amount of oxygen to transfer into the water. The higher oxygen transfer is considered beneficial for ponds with dense fish populations and/or specific breeds of fish that require higher DO levels.
Disadvantages: The small holes add pressure to the aeration system – as much as 1-1.5 PSI per diffuser depending on the type. Also, since the holes are small, mineralization of dissolved solids and biological growth can start to cover or even plug the pores. This restricts air flow and puts even more pressure on the pond aerator which can cause the diaphragms to rupture prematurely. Fine bubble diffusers often need regular maintenance and must be swapped out more frequently than course bubble diffusers. They do not mix the pond as effectively because the small bubbles do not project as far out from the diffuser and are not diffused with the same amount of force.