I can't tell you if it will or won't work in your situation, but can give some of my experiences with my tiny pre-sediment pond. If you page through this
sediment pond thread of mine till you come to the part where I built the pre-sediment pond there are pictures and descriptions.
Some problems you may run into in addition to what John F describes.....
Water exchange. High rates of water exchange can be very hard on fish. Something like FHM are pretty tough and can handle it better than larger fish but if there are huge inflows of fresh water during rain events it is tough on fish. Consider a big pond that might get a 10% water exchange during a big rain and a micro pond that might get a 10x or more. Rapid temperature and pH changes can be deadly on the fish. If you are going to make a tiny pond, consider limiting the watershed that feeds it.
Contamination. I have watched tiny BG swim upstream in a half inch deep water trail. If you have little elevation seperation and close proximity to your other pond with water flowing between, the probability that you will get contamination of other species is likely when, not if.
I'm not saying it will not work for you. Just some things I have experienced with my own tiny pond. As you will see in the thread linked above, I eventually just put a pipe between the sediment and pre-sediment ponds because of the issues mentioned and quit trying to manage it as an independent pond.
