1. Elephant Nose Fish are some bainy fish, they can be trained to do tricks, and are the only fish to conclusively show play behavior. If a ball is dropped into their cage they will bat it around with their nose, apparently just for fun. Plus... isn't that nose super cute!
2. Cleaner Wrasses - The Mahatma Gandhi of the fish world. "Peace is its own reward." - Mahatma Gandhi
These adorable little fish provide a service to everyone on the coral reef. They hang out at "cleaning" stations, and large predator fish of all kinds line up to get cleaned. The Cleaner Wrasses pick parasites off of the larger fishes body, even inside the mouth of the predator, all without ever getting eaten itself. They are so important to the ecosystem that if they are removed from the reef, biodiversity goes down as larger fish leave to go find a reef that still has cleaning stations.
3. True love last forever. Most fish release their gametes willy nilly into the water without much thought to mate choice. Courtship behavior is seen in a lot of fish, but only for the duration of the matting. After mating both parties goes their respective way, then hook up with the next fish on the reef. But the Deep Sea Angler Fish has none of that callousness going on. Male fish swim great lengths to find a female at the great depths of the deep deep sea, and once they find her they are not going to let her go. Instead they attach themselves to her body, in a true-love-lasts-forever scenario, and become the only species of fish to mate for life (as long as you exclude fish that only mate once, and I am.)
4. Parenting behavior in fish is one of those things that I find really remarkable. There are many instances of fish protecting and caring around their eggs, or even staying involved after they hatch by protecting the babies until they grow big enough to fend for themselves. My favorite are the cases where the males are the parents providing for the offspring, especially the seahorses, because the pregnant males seem so cute. One of these days I would love to write a book posing an alternative human society where the males of our species carried the children and provided human babies with their post-conception care.
5. Shrimp and Goby Fish will live together and find the situation mutually beneficial. Shrimp have very poor eyesight (and this sucks when very big things want to eat you) but they are great at digging and make awesome homes. Goby Fish have great visual abilities to see food or predators, but don't always have a place to flee too. The two organisms have developed a great partnership, where the shrimp will dig a hole large enough for itself an a Goby Fish friend. The Goby will then set outside the nest an keep watch for the shrimp. The shrimp uses its antennas to stay in contact with the fish, and when the fish sees a predator and bolts, the shrimp know it's time to go into hiding too. Both then flee to safety in the cozy den dug by the shrimp.
And they lived happily ever after!
To be continued with part two... "Pessimistic fish behavior" - Lying, cheating, and steeling happens to fish too.
