Rad, Have you looked at this thread?
http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=20;t=002890

I had built my own floating island modeled after a few I had seen on the web. Its been in for over 2 years and herons, ducks, frogs, ..etc all use iit and the small fish love it under the island and the root systems from the plants provide great cover. Nice easy project to do and it works great.

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1/10 - 1/4 acre pond plus 16 ft deep/ Plus 40 ft by 20 ft by 6 ft deep koi and fathead minnow pond next to it. Upstate NY