The Freshwater Lionfish is a most interesting fish that can be kept in the brackish water aquarium. These unusual fish are found in the muddy bottoms of mangrove estuaries and coastal waters. It is actually more of a marine fish, but because in nature it spends a good deal of time where salt waters are mixed with fresh, it is more adaptable to lower salinity levels than other marine animals.
Its common name in Australia is the Three-spined Frogfish. No one is quite sure how it received the common name of Freshwater Lionfish. They are not related to the saltwater Lionfish, sub-family Pteroinae, and fortunately they are not venomous like those saltwater Lionfish. Probably someone with an overactive imagination couldn’t pronounce "Batrachomoeus trispinosus" and needed to call them something! They are members of the Batrachomoeusgenus, which are non-venomous Toadfish.
The Freshwater Lionfish is truly an oddball fish, and rather grumpy. The names of Toadfish, Frogfish and even Stonefish give a good impression of what this fish looks and acts like. It sits very still and looks much like a camouflaged brown lump or stone, thus the name Stonefish. The broad head and large mouth are very frog-like. It also feeds very much like a frog or toad would, waiting patiently until its food comes within range and then gulping it down quickly.
The members of the Toadfish family, Batrachoididae, received their name because most of them can make a croaking sound when they are pestered or the males are courting females. It is unlikely that your pet will make this sound but you never know. Some aquarists have reported their fish grunting loudly when fellow inhabitants swim by, giving their tank mates quite a scare and making them race out of the area.
The Freshwater Lionfish gets to be quite large, reaching almost 12 inches (30 cm) in length. But despite its large size, it really doesn't need a large tank because it is quite still most of the time. It is camouflaged to blend in with its surroundings. It is peaceful, but it is a predator. Choose tank mates that are too large to fit into its cavernous mouth.