I have a loop in our pond...the only thing I can think of to aeration with a loop is that your are circulating the water and therefore your geothermal wouldn't be as effective. You want the cold water on the bottom in the summer and the warm water on the bottom in winter hence you defeat the layering wiht circulation and aeration. I don't aerate any of my three ponds and they are do fine but are spring fed and have large surface areas

21 Acres 3 great ponds all spring fed. A 3 acre a 2 acre and a 1/2 acre