Different fish appeared in different episodes. Sometimes as allies, minor roles, obstacles, or damsels in distress.
The Angel Fish appeared in The Aquarium Fix-It. She was kind enough to let to keep the seahorses safe until the crack in their tank was repaired.
During an attempt to get the Stomping Feet out of a tank with unknown inhabitants, Geo encounters 3 hungry sharks. Luckily, he spotted where their snacks were stored and gave each shark his favorite snack long enough for Geo to get the Stomping Feet out of the tank. The sharks only appeared in Stompasaurus.
Blue Mermaid's Fish Friends
Some of the Blue Mermaid's seafriends are 4 fish: pink, blue, orange, and yellow. Their role is the most minor out of all the fish.
She aided Milli on her quest to rescue Geo and Bot from the super sticky honey and being baked into Silly Bear's honey cake. When Milli had to get down the river, she used a big leaf as a raft. However, there were obstacles along the way that the leaf couldn't get through. Lucky, Little Fish came and ate a little of the leaf so it was small enough to at least get through the obstacles. Little Fish loves to eat leaves, and she also loves honey cake. She only appeared in Milli Saves The Day.
7 Little Fish
They, along with Big Bob, only appeared in Team Umizoomi VS. The Shape Bandit. After the Shape Bandit stole the bottlecap to their bottle, the team secured them in glass fish bowls. There are 1 yellow, 1 orange, 2 purple, and 3 pink fish.
He, along with the 7 Little Fish, only appeared in Team Umizoomi VS. The Shape Bandit. After the team saved the 7 little fish, he was about to fall, but he not called 'Big' Bob for nothing. He was too big to fit in the fish bowls. Luckily, thanks to a nice boy, Milli used a trophy to catch him. Talk about 'catch of the day'.