Mesmerizing Mormyrus

Mormyrus longirostris is most often called the Eastern Bottlenose, though it is also one of several fish that is occasionally referred to as a “Freshwater Dolphin.” Unlike Inia geoffrensis (the Amazon River Dolphin), Sotalia fluviatilis,(Tucuxi Dolphin), or any of the rest of the river dolphins of south east Asia and South America, M. longirostris is not actually a “dolphin.” That being said, it does track prey and keep navigate its surroundings though an electrical pulse system; while this isn't sonar like true a dolphin, it is an alternative way of tracking prey, as opposed to line-of-sight and perhaps this is what got it lumped into a dolphin grouping.

Eastern Bottlenose Mormyrus are primarily harvested as food fish as they can grow to nearly 30 inches, and there are reports of them being very delicious. They are caught both by hook-and-line and gill nets. Mormyrids in general are found in soft bottom areas where they root for worms, insect larvae and mollusks. When applying this to animal husbandry, it means they should be fed a good variety of food, and items like blood worms and black worms should be a central component of their diet. They will relish “hunting” and consuming live worms as well, but as always, be sure to get these from a reputable, clean source to prevent the introduction of unwanted pests. We have found them to be very difficult to segue onto pellet foods, even sinking ones, so be prepared to keep a good selection of frozen food on hand.

As a near bottom dwelling fish, they are generally accustomed to lower light levels, and we have found them to prefer darker environments. In regards to water chemistry, they don't seem too particular, though we keep them in an environment that is neutral to slightly alkaline, with water temperatures hovering around 79 degrees give or take a degree or two. They seem to take food less greedily in environments much outside that temperature. As far as tankmates go, keep a few things in mind. All Mormyrus have a penchant for aggression with other fish from their same genus, and should be considered “semi-aggressive” with other fish. On the flip side, Bottlenose are a fish with notoriously poor eyesight and can be easily bullied. Large, peaceful, non-electric fish are our recommendation if you don't want to keep this fish as an only fish, which would be the ideal scenario. Lastly, as was mentioned, this is a fish that gets very large, and will, in the end, need a massive aquarium, or warm climate pond.

If you're the kind of hobbyist who is always intrigued with oddball fish, Mormyrus is a great genus. These fish have great “personality” and make curious and engaging pets. For those of you who want to try keeping one yourself, head to your LFS and ask about sustainably sourced Eastern Bottlenose Mormyrus from Aquatropic!