I used to be able to get the quest fish in 20 tries or less but now I can make over 50 catches and waste half the day without getting the quest fish. The only ones I seem to get easily are surface and sky fish.
Could be that not every pond is big enough. I thought fishing power was the really determining factor (I almost always fish with 125 power or more). I thought about the biomes issue but it was never a problem for the longest time. If I'm in a snow biome that was taken over by hallow does that not count as snow anymore? That could be the only noticeable change, that I have few "pure" biomes right now in my main world.
do you have a big enough pond? and are you sure you're on the right biome for the quest fish?
Could be that not every pond is big enough. I thought fishing power was the really determining factor (I almost always fish with 125 power or more). I thought about the biomes issue but it was never a problem for the longest time. If I'm in a snow biome that was taken over by hallow does that not count as snow anymore? That could be the only noticeable change, that I have few "pure" biomes right now in my main world.