A little tedious, so here are some tips (possible SPOILERS)
In general, if fish give you a hard time, click on them. For the level that needs you to click oysters to generate planktons, it is easier if you place the coral in the positions where the same coloured plaktons will go to later. Place similarly coloured corals together, and all corals as close as possible together
Sometimes, I think that it might be nice to be able to see in a separate tab the enemies already defeated for the objective undertaken. Damage too quick to be able to see clearly the enemies and their names.
Thank you for the feedback. We do wish we could put in a Bestiary style item, but it would be a bonus. We'll see what happens with our development time after mobile is released, but no guarantees.
Thank you for the report. I'll get the developers to look into it.