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Related FAQs: Waspfishes, Lionfishes & their Relatives, Toadfishes

Related Articles: Waspfishes, Keeping Lionfishes and their Scorpaeniform Kin by Anthony Calfo and Robert Fenner, Toadfishes

Spiky characters; 

An introduction to the spiny, sluggish oddballs of the families Batrachoididae and Tetrarogidae

© Neale Monks

Ablabys taenionotus

Toadfish and waspfish may look alike, but the two families from which they come are only distantly related. The toadfish family, the Batrachoididae, is most closely related to things like the anglerfish and monkfish; while the waspfish, family Tetrarogidae, are close allies of the lionfish and stonefish. Both families occupy similar ecological niches though, and are a prime example of convergent evolution, that is, the way unrelated animals have acquired similar morphology and behaviour so that they can both do the same sort of thing. In this case, both toadfish and waspfish are sluggish, wait-and-see predators that are effectively camouflaged so that their prey cannot see them. When something tasty swims by, they lunge forwards opening their proportionally enormous mouths, swallowing the small fish or invertebrate in a single gulp.

Because they don't move much, they are at risk of being eaten by other, large fish, so both groups have evolved venomous spines that make them very unpleasant mouthfuls. Typically the toadfish have their spines on the gill covers and the dorsal fins, while the waspfish only have their venomous spines at the front of the dorsal fin, though there is some variation between species. Anyone handling these fish is at risk of being stung, and it's prudent to treat every inch of the fish as potentially dangerous!

None of these fish is very commonly seen in aquarium stores, but at least two, the prehistoric monster fish Thalassophryne amazonica and the bullrout Notesthes robusta are regularly traded and easy enough to obtain should you want to keep them. Other species turn up much less frequently, usually as oddballs in shipments of brackish water fish. It's often impossible to know precisely which species your retailer has in these cases, but since these fish all have pretty similar requirements, that's not as big a deal as it is with many other types of fish. You can safely assume that any brackish water toad- or waspfish will be fairly big, predatory, peaceful, and venomous.

Family Batrachoididae

While superficially similar to scorpionfish and waspfish, toadfishes are in fact members of a quite distinct group of fish known as the Paracanthopterygii, a large group of marine fish families. Most of them are pretty obscure, being confined to deep water, but one family, the Gadidae, is quite well known as it includes, among other commercially important species, the Atlantic cod, Gadus morhua. The Batrachoididae are one of the few families that have become quite common in shallow marine habitats, and a few species have even extended their range into freshwater too, but only a very few are strictly freshwater animals able to spend their entire lives away from the sea. The South American 'prehistoric monster fish' Thalassophryne amazonica, is one such species.

Thalassophryne amazonica isn't very large by toadfish standards, barely 15 cm long when fully grown, so its predatory habits are relatively easy to manage. A happy toadfish is one that can dig itself into the sand with just its protuberant eyes poking out above the sand, so you'll need a tank with at least a 5 cm depth of silica sand, and that pretty well rules out the use of an undergravel filter.

Thalassophryne amazonica can easily be combined with medium sized fish such as gouramis and barbs of equivalent or larger size. It is a very placid animal though, and shouldn't be kept with anything likely to harass it. In particular, because these fish stay on (or in) the substrate, you don't want to keep them with something that digs a lot or is territorial about the bottom of the tank, as is the case with many cichlids. Though Thalassophryne amazonica won't bite fish that harass them, they can (most likely accidentally) sting any fish that tries to push them around. So choose tankmates with care, concentrating on fish that will swim in the middle and upper layers of the tank.

The only other 'freshwater' toadfish you are likely to encounter are the brackish water species from South American and South East Asia. Several species have been imported, including Batrachomoeus trispinosus, Batrachoides surinamensis, and Allenbatrachus grunniens. These are all fairly large fish (from 30 cm upwards), so rather more difficult to look after and combine with other species in a community. Batrachomoeus trispinosus and Batrachoides surinamensis are also only transient visitors to brackish water from the sea, and are really best kept in marine conditions. Allenbatrachus grunniens on the other hand is a truly euryhaline fish that swims up and down estuaries in search of food, so will do well in a brackish water aquarium.

Feeding toadfishes is problematical. The marine and brackish water species feed extensively on crustaceans, so live river shrimp make an excellent staple food, if you have a reliable supply of them. But the strictly freshwater species, like Thalassophryne amazonica, appear to be much more piscivorous. The most reliable approach is to give them a steady supply of small live fish such as guppies, but conscientious aquarists are going to want to wean the fish onto dead food. This is time consuming but important, because feeding a predatory fish on goldfish or guppies doesn't give them a balanced diet and poses the definite risk of introducing parasites and bacterial infections. Just as with marine lionfish and stonefish, you need to be patient, as it may take several weeks before the fish gets hungry enough to want to eat a dead fish. You also need to be imaginative and come up with a way of making the dead fish look enticing. Dangling the food loosely on a bit of cotton or holding it with forceps can work, but obviously because these fish are venomous you need to take care not to get your hands too near the fish. Live foods like earthworms and river shrimps are certainly worth experimenting with as well.

Once the fish are taking dead foods, varying the diet is important, as in the wild all of these fishes are taking a range of prey, from aquatic insects on one day to shrimps the next and small fish the day after that. Reading up on the husbandry of marine lionfish and scorpionfish is a great way to learn about the best way to keep toadfish (and for that matter waspfish).

Incidentally, toadfishes get their name from their ability to croak. In some cases they do this if molested, presumably as a warning to predators that they are best left along because they are venomous. But at other times the males 'sing' to attract females. Definitely something for the aquarist to listen out for!

Family Tetrarogidae

The Tetrarogidae, or waspfish family, is closely related to the Scorpaenidae (the family that includes the lionfish, popular with marine aquarists) and superficially have much in common. They are compact, sluggish fish with large mouths and flamboyant fins armed with stiff spines. As their name suggests, waspfish are able to sting, and like the toadfishes must be handled with care. One peculiarity of these fish is that the dorsal fin in many species starts at the front of their head (where the 'forehead' would be if they had one). The front part of the dorsal fin can be raised, presumably to brandish the venomous spines and so scare off predators, but to a human's eye this looks very comical and to me at least reminds me of a cockatoo!

Only a single waspfish has become a regular fixture in aquarium stores, the bullrout Notesthes robusta. This fish is sometimes sold as the 'freshwater lionfish' and it does indeed have more than a passing resemblance to the marine lionfish. Like those fish it is a confirmed piscivore and can be rather demanding about food. As discussed earlier on with Thalassophryne amazonica, you should train your bullrout to accept dead foods (and it will, eventually) but be prepared for this to take some time. In the wild these fish may go days or weeks between meals, so whetting their appetite through starvation can take quite some time, perhaps 3-4 weeks. Alternatively, you could stick to using a range of safe invertebrates foods including live river shrimp and earthworms, but this is a bit risky if your supply runs out. Earthworms, for example, are tricky to find in winter. If you happen to live near a fishing tackle store, then some of the live bait, like lugworms, could be useful, too. Bullrouts are very tolerant as far as water conditions go. They do need hard, alkaline water, but the salinity level is relatively unimportant. Ideally, keep them at a specific gravity of around 1.010, but they will readily adapt to marine conditions if you want to mix them with fish like shark catfish, puffers, or scats.

Other waspfish turn up only irregularly, particularly in imports of brackish water fish from South East Asia. They are always worth looking out for, and on the whole require the same sort of care as the other fishes discussed here. Tetraroge barbata does occasionally turn up, though more often as a marine fish than a freshwater water one. It is a small species well suited to aquarium life, and adapts well to strongly brackish conditions. Like other primarily marine fish it can be picky about water quality, so ensure that the filtration and oxygenation in your tank is adequate before buying one of these animals. On the other hand, because it is a species that feeds extensively on crustaceans as well as small fish, river shrimp and amphipods can be used to feed this fish until you can wean it onto dead foods.


These fish are all very much species for dedicated hobbyists prepared to set aside an aquarium (and quite a bit of time) to their care. As with all predatory fish, their maintenance brings up the moral dilemma of whether or not is right for aquarists to feed smaller fish to larger ones. Personally, I don't like the idea of keeping a pet fish that demands a continual supply of live feeder fish. In some cases, live river shrimps, mealworms, and earthworms can work well as interim live foods, and many species can be weaned onto dead foods such as lancefish eventually, but this is by no means a certainty. Before buying any of these fish, always find out from the retailer if the fish you're interesting in is eating dead foods, or can be so adapted.

There's also the risk of being stung, as many of these fish have quite nasty stings. While not life threatening to the average person, those allergic to bee stings, for example, should treat this fish with extreme caution, and obviously young children are at more risk than adults. So while these fish are certainly fascinating and attractive beasts, they aren't for everyone. But they're definitely very, very cool!

Information boxes


Amazon toadfish, prehistoric monster fish


Latin name:                   Thalassophryne amazonica

Size:                              15 cm.

Water requirements:    Adaptable, but avoid extremes, and keep the water well-oxygenated. Do not add salt.

Food:                             Can be very picky, and prefers live fish, though river shrimp and earthworms are also taken.

Social behaviour:          Solitary, nocturnal hunter.

Breeding:                      Egg layer


Grunting toadfish


Latin name:                   Allenbatrachus grunniens

Size:                              30 cm.

Water requirements:    Brackish water essential, specific gravity around 1.010.

Food:                             Live river shrimp make a good staple, but will take dead food eventually.

Social behaviour:          Solitary, nocturnal hunter.

Breeding:                      Egg layer


Mangrove waspfish


Latin name:                   Tetraroge barbata

Size:                              10 cm.

Water requirements:    Typically marine, but will do well in strongly brackish water too.

Food:                             Live river shrimp and fish preferred.

Social behaviour:          Solitary, nocturnal hunter.

Breeding:                      Egg layer.


Grunting toadfish


Latin name:                   Notesthes robusta

Size:                              Up to 45 cm but usually much smaller in captivity.

Water requirements:    Adaptable, but brackish with an SG above 1.010 is best.

Food:                             Live foods preferred, but will take dead food eventually.

Social behaviour:          Solitary, nocturnal hunter.

Breeding:                      Egg layer.

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