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Brackish Water Fishes

Brackish water fishes are those species that inhabit the middle zone between rivers and the sea. Some of them spend their time in freshwater environments when young, and as they become older, move downstream before spending most of their time in the sea. Others are more truly brackish water specialists, being adapted to constantly changing salinity. Fish that live in mangroves, for example, need to be able to do this. Whereas most fish find changes in salinity stressful, even lethal, these brackish water specialists thrive in such environments. This gives them access to all sorts of food supplies that other fish cannot use, as well as a considerable degree of security from predators unable to handle changes in salinity. Indeed, mangroves have often been described as ‘nurseries of the sea’ because of the huge variety of fish species that spend the early stages of their life cycle in these habitats.

Among fishkeepers, the attraction of brackish water fishkeeping is primarily the variety of oddball species that are available. Given the changeable nature of their environment, brackish water fish are usually very adaptable and easy to keep. Most species will eat pretty much anything, and the middling salinity characteristic of brackish water makes it difficult, even impossible, for many of the common external parasites such as Whitespot and Velvet.
The main downside to brackish water fishkeeping has often been the irregularity with which the more interesting species are traded. In this article we’re going to look at some of the species currently on sale at Sims Tropical Fish, where you can either buy in store or you could order them online instead! Sims Tropical Fish have have a 4.8 customer satisfaction rating and also offer a wonderful price match guarantee on their fish too!

The Basics of Brackish Water Fishkeeping

In general terms, everything that applies to keeping a freshwater tank holds here. The main difference is the use of salt, which needs to be the kind used in marine aquaria. The exact amount varies, depending on the sort of environment you’re trying to replicate. A low-end brackish community, for example, would need only a little salt: 3-4 grams marine salt mix per litre, which is about one-tenth the amount used in a marine aquarium. At 25 degrees C, this would return a specific gravity of about 1.003. Such a salinity would be low enough that plants that thrive in hard water should do equally well here, including such favourites as Amazon Swords, Vallisneria, and hardy Cryptocoryne species.

A higher-end system built around a river estuary or mangrove setting would need a lot more salt. Something around one-half the salinity of normal seawater is required, which means about 15 grams marine salt mix per litre of water. This would give you a specific gravity of around 1.010-1.012 at 25 degrees C. This is much too saline for plants, so instead your tank would need to be decorated with rocks, bogwood roots, or whatever artificial décor you preferred. The upside to this level of salinity is that a protein skimmer should work well, making water quality management much easier. High-end salinity systems are most often used for large, migratory brackish water species that would, in the wild, spend part of their time in the sea.

Red Scat, Scatophagus argus

The ‘Scat’ is one of the most famous brackish water fish species. Big and basically peaceful, albeit with a robust and greedy personality, Scats have loads of character, and quickly become pets in a way few other fish manage. The Red Scat is a particular form of the Common Scat species (Scatophagus argus) that sports reddish patches on its fins. Juveniles also have a reddish tint to their scales that distinguishes them from the more yellowy bronze colour of the standard Scat. As such, the Red Scat has sometimes been classed a distinct subspecies by aquarists, Scatophagus argus rubifrons, though this name is not used in the scientific literature. Scats are very easy to keep. Juveniles thrive in low-end salinity systems, but as adults should be kept in either high-end brackish or fully marine systems as preferred. They will eat virtually anything, but a diet containing plenty of fresh green material is recommended. Scats do well as singletons, or else in groups of at least three specimens. They tend to be pushy at feeding time, but work well with very fast fish (such as Monos) that compete well. To purchase this fish, click: HERE.

Ocellated Pufferfish, Tetraodon cutcutia

This is one of the less often seen pufferfish species. It is a small (to 15 cm) and attractive species that sports a golden-brown body with mottled patches, a white belly, and a red fringe to the tail fin. Its common name comes from the dark ‘eye-spot’ on each flank, close to the base of the dorsal fin. As with most pufferfish, it is basically hardy and easy to keep, but very territorial and nippy. It needs to be kept singly, but once settled down, this fish has proven to be a good aquarium fish. It does well in low-end brackish water systems, especially tanks with plants around the edges and an open sandy area at the front where it will partially bury itself at times. Feeding is unproblematic, with most crunchy invertebrates being readily consumed, but take care to minimise the use of mussels and prawns. These contain thiaminase, which when used excessively, lead to vitamin B1 deficiency. Instead, round the diet out with food items such as cockles, white fish fillet, and insects, none of which containthiaminase. To purchase this fish, click: HERE.

Sharp-nosed Nandus, Nandus oxyrhynchus

Sometimes referred to as Asian Leaffish, these small, stealthy predators are well camouflaged animals with large mouths that they use to literally inhale their prey. Juveniles feed primarily on insect larvae and crustaceans, but as they mature, they take more small fish species. Getting them to feed is, in fact, the biggest challenge here. Live foods of some sort will be necessary at first, and may be needed in the longer term, but some aquarists have weaned them onto frozen foods. In other ways these fish are undemanding. Maximum length appears to be around 12 cm, and in terms of salinity, both freshwater and low-end conditions are suitable. Individuals are territorial and will of course view small tankmates as food. To purchase this fish, click: HERE.

Thick-Lipped Mullet, Chelon labrosus

These silvery-grey mullets do rather well in captivity, but they will grow quite big. Captive specimens reach around 25-30 cm in length, and they are also restless fish that need plenty of swimming space. In the wild, mullets sift the substrate for algae and tiny invertebrates, and will also graze on the algae that encrusts rocks and harbour pilings. Under aquarium conditions they will eat almost anything, including good quality flake food. Their natural range is astonishing, from Iceland to Senegal, and may be kept in an unheated tank without any trouble but avoid keeping them too warm (25 degrees C is probably the upper limit for long-term care). Mullets of all types are notorious jumpers, so a secure hood is essential. They are schooling fish in the wild, and best kept in small groups. Juvenile mullets adapt well to low-end brackish conditions, but adults may need to be transitioned to higher-end systems at some point. To purchase this fish, click: HERE.

Bumblebee Goby, Brachygobius sp.

Although often referred to as Brachygobius xanthozona, that species is not traded, and most specimens are in fact Brachygobius sabanus, Brachygobius doriae or Brachygobiusnunus. While difficult to identify, they are all much of a muchness in terms of care, which simplifies things for the aquarist! With adult lengths around 3-4 cm, these are tiny fish, so while territorial, it’s easy to keep groups in all but the smallest tank. They use shells and other small caves as hiding places. Salinity is not a critical factor, with both freshwater and low-end brackish water being acceptable (indeed, some specimens are even found in peaty, blackwater streams). Feeding can be tricky though, with live foods such as brine shrimp being preferred. Some frozen foods, including bloodworms, are taken, but dried foods are usually ignored. Being small and slow feeders, they compete poorly with other fish, so tankmates must be chosen very carefully. Kept well, they spawn readily, though as with other gobies, the relatively small fry are tricky to rear. To purchase this fish, click: HERE.

Mangrove Jack, Lutjanus argentimaculatus

Snappers are more usually considered reef fish, but the Mangrove Jack is one that can be found in estuaries, mangroves, and even the lower reaches of rivers. Adults can get very large, up to 1.5 m long, though under aquarium conditions even half that size would be exceptional. They are widely bred in Asia for use as food, getting to well over a kilo in weight within a year. It goes without saying that they needa very large aquarium by hobby standards. Mangrove Jacks are largely nocturnal fish in the wild, feeding primarily on smaller fish and crustaceans, and this rules them out of the mixed species set-up. Kept on their own, however, they have proven to be hardy, if nervous, fish with a certain appeal to those experienced aquarists familiar with the needs of jumbo predators. IF you would like to purchase this fish, click: HERE.

Green Chromide, Etroplus suratensis

Not to be confused with the wild-type Orange Chromide (Etroplus maculatus), the Green Chromide is a fairly largecichlid native to India, one of only three cichlids found in South Asia. Adult specimens are around 20 cm long (occasionally much bigger) and basically green in colour, with dark bands and hundreds of small silvery-blue speckles on their flanks. Their unpaired fins are tinged with red and covered with small blue speckles. Unusually for a cichlid, this is a species that thrives best in large groups, though singletons and mated pairs have been kept successfully (in very small groups, bullying can be a problem). This very attractive fish is a popular exhibit in public aquaria where it can be maintained alongside other medium-sized brackish water fishes including Mollies, Monos, Scats, and Archerfish. In the wild they are found in both rivers and estuaries, so the exact salinity does seem to matter. What is more important is water quality and a varied diet that includes algae or softened greens. If you would like to purchase this fish, click: HERE.

Freshwater Morays, Echidna rhodochilus and Gymnothorax tile

Despite being sold as freshwater fish, both these species are properly kept in brackish water. Echidna rhodochilus gets to about 30 cm long and is light brown in colour with distinctive paler patches on the sides of its mouth. Echidna species have teeth adapted for crushing the shells of invertebrates, rather than the pointy teeth seen in other morays. As such, they appreciate a varied diet that includes things like krill and rivershrimp. Morays hunt by smell, so live foods are not necessary, though in the case of river shrimp, certainly appreciated. Gymnothorax tile is a bigger (to 60 cm) species with a beautiful pattern of cream-coloured patches on a darker brown body. It is a more typical moray that consumes small fish as well as things like insect larvae and worms. Basic care is much like that of the moray species widely kept by marine aquarists, though of course a lower salinity is required. If kept at too little salinity, however, these morays tend to go on ‘hunger strikes’ so a high-end brackish water system may be needed for adults. If you would like to purchase this fish, click: HERE.

Milk Spotted Pufferfish, Chelonodon patoca

Another rarely seen pufferfish species, this is a particularly attractive species noted for its easy-going personality towards conspecifics. It is basically greyish brown with darker brown saddles across the back and numerous large white patches and spots. The eyes are golden and there is a distinctive yellowy sheen where the markings on the flanks meet the off-white colour of the belly. While tolerant, this species is reputed to be a fin-nipper, so tankmates should be chosen with care. Ideally, the species would be kept alone, as is usually recommended with pufferfish. Overall, though, the species is adaptable and not too large (up to 30 cm long) and does as well in high-end brackish water systems as it does in marine tanks. The species looks particularly good in a large tank decorated with mangrove roots that has large areas of open sand where the fish can dig, sometimes burying itself up to its eyes! To purchase this fish, click: HERE

Colombian Shark Catfish, Ariopsis seemanni
One of the most popular of all brackish water fishes is this catfish, sometimes described as the most shark-life fish the home aquarist can keep. Certainly, apart from its whiskers, the species has a very shark-like appearance. Looks can be deceiving though, as this fish, while predatory, is surprisingly peaceful. Perfectly safe with any non-aggressive fish too large to be swallowed, it is often kept with things like Scats and Monos. Shark Catfish are fairly big, getting to about 25 cm long, but highly social, and absolutely must be kept in groups. It will eat anything, including catfish pellets, but enjoys chunky fish and seafood pieces. They are restless swimmers and need a very large aquarium with lots of current. Juveniles will thrive in low-end brackish systems, but above a certain size their migratory instinct kicks in, and you may find your specimens more settled at high-end salinities or even in a fully marine system. To purchase this fish, click: HERE.

Mono, Monodactylus spp.

Monos are among the classic brackish water fishes. Two kinds are commonly seen, the Malayan Angel or Common Mono, Monodactylus argenteus, and the West African Mono, Monodactylus sebae. While quite different in appearance, basic care is similar. The Common Mono is a rhomboid fish with bright orange-yellow markings on its dorsal and anal fins, whereas the West African Mono is even taller, almost like an Angelfish. Both species have silvery bodies with black vertical banding. They are astonishingly fast swimmers and extremely manoeuvrable, being adapted to life in open water where speed and agility are needed to avoid predators. They are basically hardy fish, but sensitive to low oxygen levels. In the wild they live in large groups, swimming in the shallow water of the surf zone and around mangrove and harbours. When stressed they turn very dark, but quickly perk up again when conditions improve. Juveniles handle freshwater conditions well, but as they mature, they will need to be kept in high-end brackish to fully marine conditions. Monos are carnivorous by nature but do well on good quality flake and pellets. They tend to be very nervous as singletons, but in groups will be much more confident and outgoing. To purchase this fish, click: HERE.

Silver Scat, Selenotoca multifasciata

Saving one of the best until last, the Silver Scat is an infrequently traded but very beautiful fish closely related to the Common Scat described earlier. While basically the same in terms of care, it is a little smaller (adults are around 20-25 cm long) and shimmers with a brilliantly white silver that wouldn’t look out of place in a reef tank! There are back stripes on the top each flank that break up into smaller black spots about halfway down. These fish do very well in captivity, eating almost anything, and generally ignore their tankmates. Like all Scats, they can be pushy at feeding time, but quickly become tame, and do well in high-end brackish water communities. Adults can also be kept in marine systems. To purchase this fish, click: HERE.

This article was written by Neale Monks for Tropical Fish Finder and may not be produced without permission from Tropical Fish Finder.

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