12 Rare Saltwater & Unusual Freshwater Fish to Discover

Keeping fish has delighted enthusiasts for centuries, offering a rewarding and calming hobby. Whether you have a cold water or tropical tank, introducing some of the world's rarest and most unusual fish can make your aquarium truly special. This guide explores 6 rare saltwater fish and 6 unique freshwater fish that many even specialist shops rarely stock — and some come with a hefty price tag.

6 Rare & Unusual Saltwater Aquarium Fish

The Amusing Dr Seuss Fish

Named for their remarkable and colourful patterns, Dr Seuss Fish boast an unusual body shape and quirky faces that captivate collectors. Native to the deep oceans near the Marshall Islands, they belong to the basslet family. Despite being relatively easy to keep in a saltwater aquarium, they are incredibly scarce, with only a few dozen specimens sourced annually.

The Charming Peppermint Angelfish

Highly prized by saltwater aquarium enthusiasts, the Peppermint Angelfish is one of the rarest tropical fish worldwide. These small fish, sporting stunning red and white stripes, inhabit deep, remote reefs in the South Pacific. Found especially in the Cook Islands at depths reaching 400 feet, these elusive fish pose a challenge for divers and collectors alike.

The Colourful Candy Basslet

With striking yellow and blue hues, the Candy Basslet hails from the warm Caribbean waters surrounding Curacao. This lovely fish is relatively accessible and easier to maintain in a captive saltwater aquarium. Notably, there have been successful breeding efforts in captivity, increasing its appeal among aquarists.

The Stunning Masked Angelfish

Found along the Hawaiian Islands, Masked Angelfish dwell at depths of 100 to 300 feet in protected waters. Collection is difficult and risky due to the treacherous conditions, making this elegant fish a prized rarity among experts.

The Rare Neptune Grouper

Neptune Groupers are deeply mysterious, inhabiting very deep waters around Japan and East Asia. Prized as a local food source, they are difficult to keep in captivity because rapid ascent causes fatal decompression. Occasionally, juvenile fish appear in shallower waters and are sought after for aquariums.

The Mangarahara Cichlid

The rarest fish known, the Mangarahara Cichlid (Ptychochromis insolitus) once thrived in Madagascan rivers but now exists only in captivity. Only three known males remain: two at London Zoo and one at Berlin Zoo, highlighting urgent conservation challenges.

6 Rare & Expensive Freshwater Aquarium Fish

Freshwater tanks offer simpler setups and maintenance than saltwater, with familiar species like tetras and guppies. However, some freshwater fish stand out for their rarity, striking colours, or unusual characteristics that make them prized additions to specialized collections.

The Silver Arowana

Famous for their large, metallic scales and sleek bodies, Silver Arowanas originate from South American rivers. Some possess unique mutations causing them to glow faintly in the dark. They are among the most expensive freshwater fish, often highly sought by collectors.

The Delightful Ghost Shrimp

Once considered simply food for larger aquarium fish, Ghost Shrimp have grown in popularity as pets themselves. These freshwater crustaceans are low maintenance, breed easily, and add an ethereal charm to the tank with their ghostly translucent appearance.

The Strange Lungfish

Lungfish are linked to ancient amphibians and breathe air through lungs. Not known for their aesthetics, they are prized for resilience and adaptability, thriving in tanks with low oxygen levels. They can grow quite large, requiring ample tank space.

The Special Oscars

Oscars are freshwater cichlids renowned for their intelligence and striking appearance. They interact well with owners, often recognising human presence and eating from hands. Oscars require large tanks to accommodate their potential size and energetic nature.

The Amazing Freshwater Rays

Freshwater rays are elegant and unusual, growing quite large and requiring spacious tanks. Their unique shape and graceful movements make them standout creatures in dedicated freshwater aquariums, but they demand expert care to thrive.

The Camouflaged Freshwater Lionfish

Also called Stonefish for their remarkable camouflage, these freshwater Lionfish are adept predators. They remain motionless, resembling rocks until prey approaches, then swiftly attack. Though favoured by collectors seeking rare fish, they must be kept separately due to their predatory behaviour.

Conclusion

Choosing to keep rare and unusual fish demands commitment to responsible ownership and ethical sourcing. Many of these species have highly specialised care requirements and face conservation challenges in the wild. By selecting fish thoughtfully and maintaining them properly, hobbyists can enjoy a fascinating glimpse of aquatic rarity while promoting sustainable aquariums.

Whether you are a seasoned aquarist or a curious beginner considering exotic fish, understanding the uniqueness and needs of these remarkable species is the first step to creating a mesmerising underwater world in your home.