Donald:
Have had one installed since December, works well...found that installing it as it comes with the nylon pull string is all you need...took 3 days before koi figured it out...Very sturdy construction, so you shouldn't have a problem...
Because our's is installed outside in the elements, I did sand and apply a 2 coats of fiberglass resin, without cloth, to the roof...not sure if it was needed but now I don't have to worry about it...
The Chagoi may surprise you, he may not be the one to pull the string...In our pond only one koi pulls the string while the others crowd around to reap the spoils...It's really funny to watch the koi jockey for postion under the feeder... The puller knows that if he just pulls the string, he'll be out of position to get any pellets, so he usually moves away from string, darts back, pulls string and grabs a couple of pellets before the other koi realize what he's done...
Hope this helps, Aloha! Mike