These folks should be able to give you a good answer to your question, but remember aeration contray to what some people say is not necessary in all siuations. WHat are goals for the 20-50 acre lakes? Good fishin', then it in most cases spend the money on something else besides trying to aerate that large a body of water. Raising cows in the watershed or raising fishin the pond? then by all means aeration is well worth the cost benefit. Good luck

Greg Grimes
www.lakework.com