I bring fish into Canada quite regularly and there's not much of an issue as long as you have the scientific names of the fish, quantity and declare that they're for your personal hobby/use. The key factor in travelling aquarium fishes and/or corals, etc. is that they can't be on the CITES list as a restricted and/or endangered species.
When I brought fish back from the last MCA auction I made the mistake of mentioning that the fishes were from South America. The young customs/immigration officer looked puzzled, even when I explained that the particular fish were bred in Michigan. Twenty minutes later after speaking to his supervisor and a car search, I was on my way. First time I ever had an issue and I used to carry marine fish, corals, etc. onboard flights, etc. without any hassles and before the liquid ban.
Key thing is to know what you have and to ensure they're not endangered.
Jay