Based on the information you provided you should go with a sub-surface aeration system because you are over 5' deep. Since your power source is 375 feet from the pond I would suggest one of our systems that use a piston compressor. We use piston compressors in all of our larger system, we don't use any rotary vane compressors. With the piston compressors there is no need to run power to the edge of your pond, the air can be pushed that distance. This is a benefit of sub-surface over surface aeration plus there is no cord in the water which is a plus if you use it for swimming. If you wanted to run power to the ponds edge you may be able to go with a smaller aeration system. Using 1/2acre and avg depth of 5' you have about 842,000 gallons of water in your pond. Go to www.aerationsupply.com and look at our genAIR systems. There are many to choose from if you want to run the power to the pond. If you don't look at the genAIR-145PM. See link below.

http://www.aerationsupply.com/catalog/sub-surface-aeration/small-pond-aerators.html

As far as the muck it is possible that you have 3-5' of muck sitting on the bottom. Look at our Pond Patrol Sludge Remover Bacteria Pellets.

http://www.aerationsupply.com/catalog/po...ge-remover.html