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Keeping the “Prehistoric” Monster Fish

Prehistoric monster fishHello everyone, some of our previous blogs have certainly talked about some scary-looking and bizarre fish! I thought I would add one more to the list -the Prehistoric Monster Fish, Thalassophryne amazonica.

The Prehistoric Monster Fish has a bizarre appearance that may make you wonder exactly what it is you are looking at. It comes from the Amazon River, where it lurks on the bottom waiting for unsuspecting prey. Its tan and brown coloration allows it to blend in with its sandy environment where it often buries itself, making it nearly invisible to other fish. At barely 6 inches long, this fish boasts a wide mouth that can easily swallow large prey.  Its eyes are situated on the top of its head to allow for a perfect view while it’s buried. To make it a bit more frightening, the Monster Fish has a venomous spine on each of its gill coverings and two in its dorsal fin. Monster Fish can inflict a painful sting, and while the venom is not terribly potent, it’s best not to handle them to avoid incident.

With such a voracious appetite, tankmates can be hard to find.  You may choose to keep a species aquarium with 2 or 3 of these fish alone in the tank. Thier rather sedentary lifestyle requires little space, so a 20 long could be adequate for 2 with proper filtration. How tough are they? Some people see fish like this and always wonder as to their durability. So long as the fish are given a soft sandy base to dig down into, and a supply of healthy fish or ghost shrimp to feed on, the Monster Fish is a very sturdy tank inhabitant. Avoid any extremes in pH and keep that temperature stable (high 70’s) and they should be happy. Decoration is purely up to you, and can be minimal, since the Monster Fish prefers to hide in the substrate.

A note on feeding: As always we recommend against traditional feeder goldfish. You may consider setting up a small quarantine tank to keep a steady supply of small fish (or live shrimp) that can be medicated against bacteral infections and parasites before feeding. Though frozen foods are recommended if you can get the fish to take them, some keepers report that these fish that will only ever eat live foods and a clean and healthy supply is necessary for a healthy predator.


  1. avatar

    REALLY want one of these fish… how small an aquarium would you consider comfortable to keep 2 x specimens?

    I’ve read that they need live feeder fish – one site recommends convict cichlids… would small goldfish do?
    (Apparently, they won’t take river shrimps…)

  2. avatar

    Hi Jane, As the blog mentions, a 20 long could be adequate for 2 with proper filtration. We also recommend against using goldfish in the note on feeding at the bottom. I would recommend other live foods like quarantined and pretreated small fish like guppies or other livebearers or gut-loaded shrimp like Ghost Shrimp. Over time, it is a good idea to try to wean the fish onto a frozen diet that will be healthier and safer. Some aquarists might not have had success feeding shrimp or any non-live foods but that doesn’t mean that none of the fish will accept them; it may just take some time to get them “trained” onto the new source.

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