I dig the photos!
However, I want to point out something.
Creativity / originality will be appreciated by the voters
Your pictures are very well done, but everyone is going to take photos like that. They could be in a Chiclid photo ID book.
I am on a fourm that often has fish photo contests (for fun) and it's always the people who have action shots that normally win. For example, feeding shots, digging, mating displays, interactin with fry, fighting against a mirror, interaction with the owner, and things like that. Also, winners often show some of the aquarium and not just a close up of the fish. You may also choose to try different angles. For example, shoot from a below angle. Try shooting fish from the top, maybe swimming in an "S" curve or caught in some other interesting formation.
Your photos are very good, but it's been seen before. They pointed out that they want to see "Creativity and originality". Show them something they don't see very often and you put yourself ahead of the game!
These are just some ideas. Take 'em or leave 'em and Good Luck!
PS, your subjects are amazing!