That will probably do the trick for a .4 acre pond. I have used three pumps similar to (but different brand) that one to aerate a 3 acre pond. Three pumps each driving a double 9" round diffuser. I would say they were marginal/barely adequate but that was one 60 liter pump per acre and you would be at one pump per .4 acre. I think it would be adequate.
Be very cognizant of the depth limitations of linear diaphragm pumps (the kind you linked to). Their output drops very substantially with depth.
I have since switched to a rotary vane pump that drives all three double diffusers and I would estimate I'm getting three times the air to the diffusers. I ran the linear pumps for three years and still use one divided between my 1/10th acre
sediment pond and 1/20th acre
forage pond .
Some other links you might be interested in.
Presure vs depth calculations in aereation systems Pondmaster AP100 This is a pump of a different brand with similar construction of the one you linked to. There are aeration pictures scattered in the links provided showing my setup.
My pump upgrade to a Gast 1023 Aereation turn over rate discussion thread. 
