Theres nothing wrong with any of this build, its his choice and style of doing things and it looks really effective, i have thought about doing the same with a small pond but personally i would have put ply boards on the frame and painted black gloss. Still looks mint m8, take no notice of the haters and carry on regardless unless your stuck that is as this is MFK afterall and we are all here to help not slate each other goldfish look tasty BTW
Oh sorry dude, WELCOME TO MFK, hope you enjoy it here and learn alot too, great start on the pond dude