Not strictly the biggest fish I have never caught but last year I had a few days fishing at a small lake stocked with carp and a few kois. King of the pond was a known koi around 30lb.
On the middle day of the trip the fish showed a bit of interest in floaters but proved a bit tricky to hook. I spent quite a while putting my bait in front of the King koi who was very visible, easily recognisable and markedly bigger than anything else in there. Despite getting the presentation inch perfect it never showed the slightest interest and only took two free floaters all day. On the final morning it had warmed up a lot and the fish were more active on the top. Noon was kicking off time so it was a bit of a race to get fish up. After a couple of small fish early on I had another go at the top end of the lake which was popular with King koi. With 30 mins to go I saw a decent fish, probably around 20lb and got the bait right in front of it. Perfect take. Swish...... Missed it?! %@# not happy as it looked a sure thing.
10mins to go before leaving and King koi is approaching the bait. Stops dead and then slowly, so slowly lifts up in the water. It's gonna take it I thought. It just looks right. Mouth opens and it starts gobbling at the mixer. Steady boy, this is it. Slowly, the mixer bobs and twirls and bobbles towards the sucking mouth. It's gotta take it, surely its going to have it? And it did. Down it went. Steady, steady don't strike too soon. So I waited an eternity, much much longer than with the earlier take. And as the fish gently submerged I hit it. Swish...... missed, bait in the tree above me. Arrrrrrrrggggggghhhhhh. And then I went home.