Yes, Fish Sleep. But...

[NeonBlueLeon]

Do they dream?
 
Here's an article I found interesting while procrastinating on my chemistry work: click me!
 
About 3/4s of the way down, where he talks about fish learning, is what interested me.  What do you guys think?  Do fish dream?  What do you think they dream about?  If they dream, perhaps it's of old tanks/habitats.

 

[DreamertK]

Probably, though their brains are much smaller than ours, so their visual cortex is limited along with their memory and most certainly logical ability. With angelfish it's possible that there is a strong memory of their partner, but perhaps it might also be hormones secreted in the water such as oxytocin that females release in their brains that lead to a desire to build relationships with a partner. My fish don't ever seem to recognize each other, though I cant say for certain if that's really the case. Though I can say that my fish's memory is bad. Their tank doesn't change much, but whenever I turn on the light and wake them up its like they have no idea where they are. Though I do suppose they have a good memory for food in that they know that if I'm next to the tank they're probably going to be fed, and that usually I have worms in my dispenser that they'll nip the end of.
 
Maybe they dream of a big juicy worm, because usually after I wake them up they get fed.

 

[NeonBlueLeon]

Haha! I hadn't thought about them dreaming of food, though that is a big possibility, if they dream.  How about a dream where it's raining micro pellets?
 
I have these two female guppies that clearly can recognize each other.  I bought them from the same tank at the fish store, and they always hang out together.  They swim together, scavenge together, sleep together.  It's cute. 
I recently (about a week ago) introduced another female guppy of similar appearances.  Although they do swim together occasionally, the two original ladies clearly spend more time together. 
For anyone interested, the two girls are named Abby and Betty.  The new girl is named Nina.

 

[DreamertK]

My shrimp would love that, but my fish have an extremely high preference for the worms.