Create new / custom fishing spot / water in debug for fishing

I tried using debug / tile picker mod to make myself a small lake close to a base i wanted to use and the water seems to work well, i can cast fishing rods in it, gather the water for purifying etc but there are no fish ripples. i have been casting my fishing rod for 3 days straight now and 0 hits. it only work when adding chum to the water so there seems to be something missing to get it to work naturally.

anyone has an idea on what is missing and how to fix it? has anyone ever created a working fishing spot in debug?