The Blobfish or Psychrolutes marcidus is without a doubt in one of the ugliest fish in the ocean. These saltwater fish have what resembles a large nose in between two eyes and almost seem to be frowning! I guess with an ugly mug like that you would be frowning too. This deep sea fish is often found at extreme depths off of the coasts of Tasmania and Australia. For this reason the Blobfish is rarely seen by the human eye.
I sorta agree with Olympia. They keep one of the hardest fish to keep, but ONLY them. I still love them, though :D they're sorta like a cross between Bettas and tetras. Varied color patterns and occasionally aggresivness of Bettas, basically giant tetras :D horrible comparison, I know....
Edit: I want to make a meme out of that blowfish picture. Saying what? "please kill me..." I mean, seriously, that thing look depressed.
Barreleyes or Macropinna microstoma is arguably the weirdest fish in the world. This stranger creature has a translucent head that you can see right through! Their eyes rotate upwards in their heads giving them the ability to actually see the area above itself! That's right, these deep sea creatures actually keep an eye on potential predators or food that is swimming in waters above them.These pictures were taken off the coast of California, but little more is know about the habitat of this rarely seen fish. Barreleyes can grow to only about 4.4 cm and are also known as Spookfish. They are found in waters of 16 to 1015 meters deep.
I think they need pretty clean water. But other than that, they do pretty much gobble up food. Compared to other freshwater fish, they are reasonably harder to keep, though. Partially because they need a 125 gallon tank for 5-6 of them, to grow properly.