If you have warm water species do not be concerned about overheating your water. If you have cool water species and the population is not high fish such as SMB and YP will also be fine unless your pond is very shallow and you are over circulating for which you can easily monitor during summer heat. Cold water types can easily get overheated with bottom diffused aeration if not done correctly.As far as diffuser placement in deep areas that can depend on the age and organic load of the pond prior to aeration. If for example you have a small area of very deep water and the pond is perhaps 10 plus years old and heavy organics this can act as a nutrient sink and collection point for negative things. Then consider staying out of that area unless you are willing to start the aeration up very slowly. There are general guidelines for most startup procedures but often is necessary to custom tailor a startup depending on several factors based on your pond specifics. I have old deep ponds take months to expel negative gasses where the pond owner wanted the stations on the bottom from the start vs slowy moving them deeper or slowly starting the system.Seems the more mature fish are the first ones to belly up when a system is started improperly.Bill and Shawn gave you great information ! ( and Makoclay perhaps got luckey) \:\)