Love them or hate them, those new jelly fish are here to stay. I have tried to study their behaviour to see which levels they are a help and which ones they are no help at all.
Firstly some general points:
These fishes behave differently from what the old fishes used to do. We have to relearn the mechanics and change our strategy accordingly. The use of the new fishes is now part of each level design.
Because of the above the videos posted on YouTube are not much help any more.
The best help at the moment we can get on how to use the new fishes is to turn on hints in the game and follow the suggested moves for levels we are stuck on. Right now, (March 2025 ) the game designers want players to get used to the new fishes and will help by suggesting the best possible moves in most levels to incorporate the fish. Many move suggestions now are to create a fish. This may change in the future, but I have found that at the moment the game hints will help.
Making a combo with the fish:
Fish+ colour bomb is a great combo, especially on jelly levels.
Fish+wrap or fish+stripe no longer works, so don't make such combos.
Fish+Fish is good for some levels as it will create 3 fish, so it is good near the end of a jelly level
I have repeatedly tried this and have found that in all instances the new fish do reliably clear the last jelly on the board. Other blockers may however not get cleared as a last move, and fish+wrap or stripe also may not work.
One warning: The new fish will NOT attack any other fish. So there will be no fish eats fish cascades, and even if the last jelly or last candy underneath a dragon is a fish no fish will go for it, so you will need to use other means to clear those spaces