Lacey Bill gives good advice as always he knows his stuff! The Eco plus pump for air in your type of pond may work very well. I have used one for 4 years now in 8 foot of water so in 4 foot it should do quite well and it won't break your bank. Although in 3 to 4 foot of water I am not really sure how much turn over your going to get?? I thought I read somewhere on this forum that in ponds that shallow there really is not a a good reason to run air? Dont quote me on that though! It just can't really do what it's meant to do and that's pull your water up and turn it over. If you do run it I would try and setup 2 or 3 differnt spots with air to maybe get better movement of your entire water body.
RC
