People have enjoyed keeping fish for a very long time. Whether cold water or tropical, setting up a tank and then putting in some gorgeous colourful fish, can be a very rewarding experience. Watching fish swim around is relaxing and after a hard day at the office, a very welcomed pass time. These days there's a great choice of fish around, but some are a lot harder to get hold of than others and this is especially true if you want to stock a tank with more unusual or rare fish.

Here is a list of 6 exotic tropical fish and 6 of the rarest and most unusual freshwater fish that you may not be able to find even in specialist pet shops. If you do find them, be prepared because some of the fish carry a hefty price tag.

6 Rare & Unsual SaltwaterAquarium Fish

The Amusing Dr Seuss Fish

Dr Seuss Fish get their name from their amusing and strange colour patterns. They also have a pretty weird body shape and funny looking faces which gives them real loads of appeal. They live deep in the oceans around the Marshall Islands and are from the “basslet” family.

When it comes to keeping Dr Seuss Fish in salt water aquariums, they are prized by real collectors as being quite easy to keep – however, they are pretty hard to find with only a few dozen specimens being carefully sourced from the depths of the ocean every year.

The Charming Peppermint Angelfish

Most avid fans of salt water aquariums will tell you the charming Peppermint Angelfish is one of the rarest and hardest tropical fish to find in the world today. These fish are simply gorgeous with stunning red and white stripes. They are found in the South Pacific but only in very few locations and at great depths.

Scuba divers in the Cook Islands who wreck dive at depths of 400 feet might just come across these gorgeous fish because they like to live along deep, remote reefs which can often be complex underwater habitats.

The Colourful Candy Basslet

This really lovely looking fish boasts stunning yellow and blue colours and is found in the warm waters of the Caribbean more especially in the ocean around Curacao. They are really easy to keep in salt water aquariums and to date there has been a certain amount of success in breeding Candy Basslets in captivity.

The Stunning Masked Angelfish

This stunning and elegant fish can be found in the seas around the Hawaiian Islands more especially along the Hawaiian Chain – but you need to know just where to look. Masked Angelfish live at depths of anything from 100 to 300 feet and the waters around Hawaii are protected. However, where these stunning fish are found, it is still possible to collect them, although it can be quite a challenge that many people will not even attempt to do because the waters are so treacherous.

The Rare Neptune Grouper

Neptune Groupers are very rare fish which are incredibly hard to come across in captivity. They can be found in very deep waters around Japan and East Asia where they are prized as a food source. These fish live so deep in the ocean that when caught if they are brought to the surface too quickly, it can prove fatal to them – the fish die of decompression!

The Neptune Grouper is really hard to find but not impossible because some juvenile fish are sometimes caught in shallower waters of the region which are then sold as aquarium fish.

The Mangarahara Cichlid

This has to be the rarest fish in the world and is found in the warm waters of Madagascar. There was a time when the Mangarahara cichlid (Ptychochromis insolitus) lived in the Madagascan river from which it got its name, but sadly their habitat dried up and today there are just three of the fish left - and they are all male – two can be found at London Zoo's aquarium and the third on is in the Berlin Zoo.

6 Rare & Expensive Freshwater Aquarium Fish

When it comes to freshwater aquarium fish, there are some rare and very expensive ones too. Freshwater tanks are a lot easier to set up and maintain than tropical aquariums with lots of people keeping tetras, guppies and lovely goldfish in them. However, there are some rather stranger fish around too, some of which boast amazing colours and others would look more at home in a tropical tank, but are indeed freshwater fish.

The Silver Arowana (Arawana)

This is a truly strange fish because it has such large scales, its body is slim and the fins are wide but short. They can be found in rivers in South America with one species of the fish having developed a slight mutation which causes it to glow in the dark. The Silver Arowana is one of the most expensive fish around – that is if you can find them!

The Delightful Ghost Shrimp

The Ghost Shrimp is a freshwater species which in the past was considered to be food for larger aquarium fish. However, they have now become very popular to keep as pets themselves because they're really easy maintenance and very easy to breed from – they thrive really well and have a certain ghostly appeal to them

The Strange Lungfish

This species of fish actually has lungs and is thought to be related to amphibians of times long past. Lungfish are not the prettiest fish but they are incredibly hardy, surviving in tanks which have no aeration or very little air. They are great pets to keep and can grow pretty big if they are kept in larger tanks.

The Special Oscars

Being part of the cichlid family, the Oscar has earned itself a special place in the fish keeping world. The bigger the tank they are kept, the bigger these fish can grow ending up an impressive size indeed. They are wonderful fish to keep as pets and like to eat out of their owners hands – they respond really well to people on the other side of their aquarium glass. Oscars are brilliant freshwater fish to keep and over time have gained a huge following of avid collectors.

The Amazing Freshwater Rays

These freshwater rays are truly unique and can grow to be pretty large. You would have to know how to keep these elegant rays and you would also need a larger than average tank to keep them in so they can move around and thrive.

​The Camouflaged Freshwater Lionfish

Also known as the “Stonefish”, Lionfish are the predators of the aquarium world. They have the ability to hide extremely well and are armed with all the right camouflage they need to expertly do this. They sit absolutely motionless and resemble a rock until their prey gets too close to them and then they pounce. They have become really popular with collectors who like to keep more usual fish in their freshwater tanks – but the Lionfish has to be kept away from other fish or they will eat them!