If you’re like many aquarists out there, the thought of having a perfectly aquascaped tank with a brightly colored school of fish bores you to tears. You want something different. You want a unique aquarium, filled with oddball fish that people can’t help but notice the moment they enter a room.
Luckily, the aquarium trade has no shortage of strange freshwater fish, with many looking almost like they’ve been plucked from an alien world or the deepest depths of the ocean. There are fish with no eyes, fish with transparent bodies, and catfish that spend their lives swimming upside down.
Listed below are five oddball fish you can add to your aquarium.
Blind Cave Tetra
The blind cave tetra is a true oddball, having no eyes and an almost albino coloration. Found living in lightless caves in Mexico, these fish lost their eyes over thousands of years as they existed in complete darkness.
But don’t think having no eyes would limit these fish in any way. They are perfectly capable of navigating an aquarium using their lateral lines, which can detect movement, pressure, and vibrations. It’s always fascinating to watch blind cave tetras swim around an aquarium, avoiding obstacles and hunting for food.
The first time someone sees an upside-down catfish, they often stop and ask, ‘is that fish alright’? And while it can be jarring to see a fish swimming upside down – especially since most other fish will only do this when critically ill – upside-down catfish spend most of their time swimming upside down.
It’s thought their strange swimming behavior developed to help them better hunt insects at the surface of the water. But regardless of why they swim upside down, these fish are a great oddball fish to add to any peaceful aquarium.
Ghost catfish are one of the strangest fish on this list, having a completely transparent body. Some fishkeepers have described them as little swimming skeletons attached to a fish head. Only during illness or near to death do their bodies take on any coloration, turning a milky white during these times.
Unfortunately, ghost catfish tend to be somewhat shy in aquariums, and without plenty of elevated hiding places, ghost catfish will spend much of their time in hiding. However, with the addition of plenty of plants to filter the light, they can be enticed to come out more often to display their strange appearance.
Black Ghost Knifefish
A truly strange-looking fish, the black ghost knifefish appears at first glance to have no fins. But it does have an anal fin, which stretches from the belly to the tail. This elongated fin gives it a unique swimming style, where it almost seems to glide around an aquarium.
And if that wasn’t enough to set them apart from other aquarium fish, they are also a weakly electrical fish, producing electrical impulses. However, they discharge less than a volt, making them no danger to a fishkeeper.
Black ghost knifefish are nocturnal and until they get settled in an aquarium, they will spend most of their time hiding. To solve this problem, some aquarists add a ‘black ghost knifefish tube’, which is a clear tube for the fish to hide in, but where they can still be viewed during the day.
Amazon Leaf Fish
Does the idea of having a leaf swimming around an aquarium sound interesting to you? Then the Amazon leaf fish might be the perfect addition to your tank. Their incredible camouflage helps them to closely resemble a dead leaf in their natural habitat, which enables them to hide from predators and sneak up on small prey.
Amazon leaf fish are voracious predators and will eat smaller fish in an aquarium, though juveniles primarily prey upon invertebrates. And with jaws that can extend up to an astonishing 60% of their head length, very few small fish are safe around them.