Surface v.s. Bottom Aeration

It’s All About Gas Exchange

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– Joe Holz, Outside & International Sales

I recently gave a talk on aeration at the Northern Aquaculture Demonstration Facility, near Bayfield, WI, which is part of the UW Stevens Point campus.  This event had several attendees that ranged from the pond hobbyist to full scale production aquaculture.  The talk included an overview of what aeration is, the benefits of aeration, and the types of aeration available.  During the Q&A portion, much of the discussion revolved around the question of “What type of aeration is best?”.  This type of question is not unique to aquaculture and is one we field routinely.  The short answer is “It depends,”

northern-aquaculture-demonstration-facilityAeration is all about gas exchange.  There are many ways to accomplish this and some work better in different applications.  Each pond is different and each application is unique so simply saying one type is always best would be too simplified and often inaccurate.

There are 2 main types of aeration, surface and bottom.  In general, Surface Aeration is best in shallow water applications or when large amounts of oxygen are needed quickly.  Splashing style surface aerators physically break apart the water, creating more surface area for the gas exchange.  This can actively add large amounts of oxygen to the water very quickly and is ideal for shallow water applications as surface aerators can work in minimal water depths.  We typically recommend surface aeration in ponds 8’ deep or shallower.

UW-Stevens-Point-Diffused-AerationBottom aeration is best in deeper water applications.  The rising bubbles through the water column entrain vast amounts of dead, bottom water and carry it to the surface where the harmful gases (mostly methane and sulfur compounds) can vent into the atmosphere and oxygen can enter the water.  The efficiency of this style of aeration is directly proportional to how much water the bubbles carry.  Thus, deeper water allows for a better circulation using bottom aeration and each diffuser can move more water the deeper it is placed.  We typically recommend bottom aeration in ponds deeper than 8’ deep.

As with most things in life, there are exceptions to these general rules and those tend to be based on the application and use for the pond.  For example, surface aeration is often limited by power location as power cords can only be run so far.  For ponds that are great distances away from power, bottom aeration would be better as air lines can be run up to 1 mile from the power source.  Also, in ponds where people or pets will be entering the water routinely, bottom aeration may be a better choice as no electricity is in the water.  On the other hand, surface aeration is best when oxygen is needed quickly (such as a fish kill event) even if the pond is very deep.

One size does not fit all when it comes to aeration type and layout.  We, at Kasco, specialize in providing the best type of aeration for your specific application.  We are more than happy to help you with style, size, and placement of the best type of aeration for your pond and pond use.  Please contact us and let us help you improve your pond the best way possible.

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