A Guide to Keeping Brackish Water Fish

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A Guide to Keeping Brackish Water Fish

Postby fishnoob » Wed Sep 02, 2009 10:08 am

"Why keep brackish fish? Aren't they a dull bunch of brown, silver or speckled fish? And don't they need huge tanks in excess of 400L? There's not much choice with them either - you can only choose from like four species. And you can't keep any plants!" is a common question asked by most who have not experienced brackish tanks yet - indeed most of these 'myths' about brackish fish are just that, myths.

Brackish tanks can contain some of the most unusual and entertaining fish around - a fish that has half it's eyes submerged, and the other half sticking out of the water, a fish that can climb out of the water and hunt on land, a fish that shoots out jets of water to knock insects off leaves and catfish that look like Jaws. And if that isn't for you, there are a variety of small colourful species - a bright orange cichlid, a striped goby and even some of your favourite freshwater species that actually do better in brackish. There are even several invertebrates that can be kept in brackish tanks - including shrimp and snails.

"What size tank do I need then?" I hear you ask. You can keep small brackish species in tanks as small as 35-60L, but a very average sized 240L is best for a nice brackish community tank. If you want to keep some of the larger species 400-800L is a nice size.

"What do I need? Do I need all that marine equipment and all that freshwater equipment? That's a waste of money!" you then ask. You need all the basic freshwater equipment - filters (preferably external, or in larger aquaria, sump), heater, lighting (you're not growing high lighting plants or corals so you can go easy on this one to save cash), substrate, etc. But, you also need a few marine tools - in particular - a marine test kit (the API one is the best), marine salt, a protein skimmer (this is only needed if your tank's SG is above 1.010) and a hydrometer (it's cheaper than a refractometer, and you don't need a refractometer for brackish aquaria as brackish fish aren't too particular about that sort of thing.)

"I got all those things. Now can I keep plants in there?" you ask. You can, indeed. A lot of common freshwater plants - bacopa, java fern, elodea crispa, anubias, crypts, vallisneria, crinum and java moss will generally be fine at low SG - 1.002 to 1.008, however, growth will slow down even at those low SG. Java fern and java moss are the most hardy of these to SG. At higher SGs, you can add mangroves. There are several species available and they will tolerate nearly all SGs from pure freshwater to pure marine. Bear in mind some grow large, so be careful. Plastic or silk plants are also an option.

"Okay, I added my plants, now what do I do?" you then say. You can fishless cycle it, just like a regular freshwater tank, and then add some fish or inverts.

"Are there any good invertebrates for the brackish aquarium?" Of course! Here are the most common species:

Shrimp - There are three species of freshwater shrimp that do fine in brackish aquaria. The mandarin shrimp, C. cf.propinqua, the amano shrimp, C. multidentata, and the ghost shrimp, Palaemonetes paludosus. They do best in an SG of 1.006 or below. All grow to 5cm and can be mixed with most smaller brackish species of fish, but it's a good idea to avoid knight gobies. There are two final species of shrimp, the Hawaiian red shrimp, Halocaridina rubra and the rednose shrimp, Caridina gracilirostris, that are commonly found in brackish waters in the wild. Halcaridina rubra is perfect for a nano brackish tank due to the fact the largest specimens are only around 2cm, however, this size makes it unsuitable for mixing with nearly every brackish fish. Sadly, it is unavailable in the UK, and if you want it, you must import it from Germany. Caridina graciliorostris is far more common and is often sold as a freshwater shrimp, when in fact it does better in brackish.

Crabs - The common blue leg hermit crab, Clibanarius tricolor, is a reef crab that will do fine in an SG of as low as 1.010, right up to 1.025. It can be mixed with most fish. The red claw crab, Perisesarma bidens originates from mangroves and does well in an SG of 1.005 up to 1.015. The fiddler crab Uca sp., is also a mangrove crab and enjoys the same SG. Neither species is really suitable for mixing with fish, as both need access to land. However, you may mix both species together if you wish.

Snails - Nerites are the main option here, with most aquarium species including the tiger and red onion being fine as high as SG 1.005, and the nerites from the genus Clithon being fine up to SG 1.012. Malaysian trumpet snails will tolerate all SG from 1.000 up to 1.025 and so are perfect for brackish aquaria and can be found in salty water in the wild.

"Now what fish can I keep?" you ask. Well, there's several available...

Mollies and Sailfin Mollies - Poecilia sphenops and Poecilia latipinna and Poecilia velifera are all good options and come in a range of colours - black, gold, dalmation and yellow. They are often seen in freshwater tanks but will do better in brackish. They are one of the hardiest brackish fish and tolerate most SG from 1.000 right up to 1.010, and latipinna and velifera (as well as the 'black molly' hybrid) will be fine up to 1.025 (and so can be kept in nearly all brackish aquaria except those which have predatory fish in them.) Indeed, they are sometimes kept in marine tanks, and in the wild often live in waters with higher amounts of salt than marine! They are also beneficial to the brackish tank as they eat algae. They like lots of vegetable foods such as algae wafers in their diet, but will also enjoy the treat of some live or frozen foods such as Artemia, brine shrimp or bloodworm. A minimum of 60L is best for sphenops, but latipinna and velifera are best in 100L+ tanks. and they can be mixed with most other brackish species. Latipinna grows to around 7-10cm, Sphenops and the 'black molly' grows to around 5-7cm, and Velifera grows to 10-15cm.

Bumblebee Gobies - Brachygobius sp. are a good addition to the brackish community tank. They mix well with most brackish fish even aggressive ones like the figure 8 puffer. They are best not kept with larger species however, such as scats, monos, four eyed fish, columbian shark catfish and archer fish. They require live foods at first in general, but can sometimes be weaned onto dead foods. They like low SG, around 1.003 to 1.005 is perfect for them. They grow to 3-5cm generally, and are not shoaling fish and are territorial. However, like most small gobies, they are interesting to watch in small groups. Add lots of hiding places like upturned flowerpots, rocks and plants, so they can hide from one another or tankmates of other species if necessary. As they are bottom feeders, a fine substrate of sand or fine gravel is best for them. A minimum of 40L is best for them.

Silver Monos and African Monos - Monodactylus argenteus and Monodactylus sebae are two large brackish species. The former will grow to 20-25cm long and 15-20cm tall and the latter will grow to around 15-20cm long, and 20-30cm tall. They are shoaling fish, as well. For these reasons, both species require a tank of at least 550L in size, preferably 700L or over. They can be mixed with other brackish species as well as one another - mollies, scats, archerfish, orange chromides, shark catfish and green chromides all make good tankmates for the monos, but bear in mind some of those fish do not make good tankmates for one another - shark catfish will consider mollies and orange chromides lunch. Monos require some form of vegetable matter in their diet - as with mollies algae wafers are happily taken, as are meaty treats such as frozen or live foods. They are always active fish and fun to watch and like an SG of between 1.010 to 1.025. They are often kept in pure marine tanks, but cannot be kept in pure freshwater tanks like mollies can, as they will die if kept in that way. It is a good idea to increase the salinity of their tank slowly as they grow.
These are silver monos in their natural habitat.

To be continued very soon with info on...
- More fish for the brackish aquarium
- Photos of all the fish species
- Inverts for brackish aquaria
- How to maintain your brackish tank once it's set up
Last edited by fishnoob on Wed Feb 17, 2010 11:32 am, edited 1 time in total.

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Postby fishnoob » Fri Sep 04, 2009 5:24 pm

Knight Gobies - Stigmatogobius sadanundio are a small predatory goby that reaches 7-10cm. They generally tolerate a wide range of SG of between 1.003 and 1.015, but can often be acclimated to even higher SG. They will consider very small brackish species like bumblebee gobies and guppies as suitable prey. Knight Gobies are also known as Fandancer Gobies. Like bumblebee gobies they are a non shoaling species and are rather territorial with one another, but if you have a suitably sized aquarium, they are more interesting to watch in a group. They require a minimum of around 60L. They mix well with most brackish fish, from sailfin mollies and orange chromide to monos and scats. They enjoy some meaty foods in their diet such as bite size chunks of prawn or whitebait and frozen bloodworm with the occasional treat of live foods.

Targetfish - Terapon jarbua are medium sized (10-20cm) brackish fish that feed on plant material and invertebrates in the wild. They will prey on smaller fish given the chance, but will do fine alongside similar sized fish such as monos, scats, archerfish and green chromide. They are getting increasingly more common in aquatics stores and make fine additions to larger brackish aquaria. They are generally white fish with brown/black lateral stripes. In captivity they are not picky eaters will happily feed on most foods you give them, but a good balance of both meaty foods and vegetable foods shuld be provided. A tank of 300L should cater for a targetfish well while leaving some room for tankmates. They are territorial and ideally should not be mixed with others of their own kind, but in a large enough tank this could be possible. They tolerate an SG of 1.010 up to 1.015.

Guppies - Poecilia reticulata are a small insectivorous fish sold for freshwater tanks, but like mollies they can tolerate an SG of higher than marine if slowly acclimated (however I believe they are at their best in brackish conditions)! They have been known to do better in brackish than in freshwater. They are good additions to the smaller brackish tank and are a shoaling species, and make good companions for mollies, bumblebee gobies and dragon gobies. They readily accept commercial foods but enjoy live foods, in particular, mosquito larvae. Some vegetable food such as peas or algae wafers are also a healthy addition to the fish's diet. They require a minimum tank size of around 60L. The males are usually 4-5cm, and the females 5-6cm. They tolerate a wide range of SG, from 1.000 up to 1.015.

Orange Chromides - Etroplus maculatus is a small, inoffensive cichlid that grows to around 6-10cm. It is not a shoaling fish technically, but enjoys being in a pair, and is very tolerant of others of it's species outside that 'pair'. A 125L is the minimum for keeping a small group of 4 or 5 of these. In the wild they act as a 'cleaner fish', eating parasites and dead skin off larger fish (including the closely related Green Chromide), in addition to it's diet of aquatic invertebrates and most other foods that come it's way, being a very opportunistic species. For this very reason, they make good additions to the fish tank - they accept commercial foods, are peaceful, are colourful, are small and show the interesting behaviour characteristic of cichlids. They like an SG of between 1.005 to 1.015. They can be mixed with most other brackish species, including their larger relative the Green Chromide, and also small fish such as guppies, mollies and small gobies. The pictures shown below do not do the Orange Chromide much justice as the ones below are most likely newly imported specimens - when kept in the right conditions such as in brackish aquaria, they will quickly colour up into a stunning bright orange.

Green, Ruby and Silver Scats - Scatophagus argus, Scatophagus argus rubrifons and Scatophagus multifasciatus are the three most common 'scats' in the trade. The first is green/silver and spotty, the second is silver with a reddish tint and striped, and the third is silver and striped. All three are relatively easy to get hold of, but the first is the easiest in the UK. They are very easy to care for, as are tolerant of most water conditions and will eat almost anything from aquatic plants and shrimp to worms and even the excrement of tankmates. Indeed, in the wild, they are known to live around sewage outlets - some specimens eating human waste. However (just as with monos and mollies), be sure to give them good amounts of vegetable matter in their diet - spirulina flakes should be fine, with the occasional vegetable in there too. They do best at an SG of 1.010 up to 1.025, but will generally be very tolerant of SG. The first two reach around 20-25cm in length, and the last can reach 30cm in length, so make sure you have a large tank and efficient filtration. They are mildly territorial, but aggressive behavior beyond simple flaring is rare. All three species mix well with each other, knight gobies, sailfin mollies, monos and green chromides.

Green Chromides - Etroplus suratensis resemble the Central American T-bar cichlid in appearance. They like an SG of between 1.005 and 1.015. They will readily eat any plants in the tank, and are primarily herbivorous, so be sure to feed with plenty of spirulina and vegetables - with the occasional meaty treat of frozen bloodworm, or an earthworm or two. They grow to around 25cm in length and can be territorial towards others of their own kind (unless they are a mated pair), as well as other brackish cichlids (excluding the orange chromide, which they will tolerate.) They require a large tank with good filtration, and can be kept as tankmates for most other brackish fish such as sailfin mollies, knight gobies, monos, scats, violet gobies and black mollies. They will even get on well with fish that are small enough to eat due to their herbivorous diet! They are a bit more of a challenge to obtain than the orange chromide. They require a minimum tank size of around 240L, but will want something larger if you wish to mix them with other fish species.

Four-eyed Fish - Anableps anableps, Anableps dowi and Anableps microlepsis are the three species of four-eyed fish in the hobby. These amazing fish keep half their eyes above the water, and half below. This means they can look out for predators and prey above the water and below the water at the same time. They all come from mangroves and estuaries, with A. dowi coming from Central America (primarily Mexico), and A. anableps and A. microlepsis coming from a band of coast in South America at the mouths of important rivers including the Amazon and the Orinoco. A. anableps is the most common species in the fishkeeping hobby. The other two species are relatively rare in comparison. All three species grow to 25cm and like some air space above their tank. Their aquarium needs a tight-fitting lid as they are known to jump out of aquaria. They require good filtration, preferably in the form of a good external like an FX5 or an Pro III. They feed relatively easily, and will readily take most meaty foods such as frozen bloodworm, tubifex, prawn and most kinds of frozen fish or shellfish such as mussels and whitebait. Most can be weaned onto flake foods, but be sure to give them a good, meaty flake. The best tankmates for four-eyes are archerfish, but they will also do well alongside monos, scats, knight gobies, sailfin mollies and chromides. Very small tankmates like bumblebee gobies will be quickly devoured. They like an SG of around 1.005 to 1.015. They should be kept in tanks in excess of 240L, but something larger is recommended if you want to mix them with other species of fish. Their peculiar appearance may suggest they are gobies - however, they are actually cyprinodont livebearers (just like mollies and guppies), not gobies.

Mudskippers - Periopthalmus sp. are interesting fish that walk on land. They most likely resemble the species of fish that evolved into amphibians a few hundred million years ago. They live in mangroves in the wild off the coasts of East Africa, South-east Asia and North Australia. They require tanks that are only filled up to about 15-30cm high, with either a slope leading to a sand river bank out of water, or a piece of cork bark or a similar object floating in the water. You can also use the filter outlet to create a small waterfall if you wish. The care of these fish is extremely complex so please read up about them if you want to keep them outside of this short paragraph. They are carnivores but will readily accept most meaty food such as frozen fish and shellfish, as well as bloodworm and tubifex. They readily enjoy terrestial live foods such as crickets, locusts, mealworms, earthworms and waxworms. They can sometimes be weaned onto meaty flake foods. They grow to 10-20cm, dependant on species. A minimum sized tank of 180L is required and an SG of 1.005 to 1.015. They are best kept in a species tank, but you can mix them with similar fish that are too large to eat if you would like to, such as knight gobies, if you have sufficient space. As with all gobies, mudskippers are midly territorial towards one another.

Columbian Shark Catfish - Arius sp. resemble sharks, which give them their common name. They are tankbusters, as they can grow to 60cm in size in the aquarium. Therefore, they need sizeable tanks of 800L and above. They enjoy being in small groups rather than alone. They are relatively peaceful, but due to their size, tankmates should be large - four-eyes, monos, archerfish, scats and green chromides will all work well. They originate from the west coast of the Americas, stretching from California down to Peru. They live in estuaries, brackish rivers and in the open ocean. They like an SG of 1.010 to 1.025. They will only eat meaty foods such as meat based pellets, pieces of frozen fish or shellfish and prawn.

Archerfish - Toxotes jaculator is a large fish that grows to 25cm, and likes to be kept in a group of at least 4. Therefore, it needs a tank of 500L or above. It can be mixed with columbian shark catfish, monos, scats, four-eyes, green chromides, knight gobies and sailfin mollies. It originates from the mangroves of southeast asia, and feeds by shooting jets of water from it's mouth to insects sitting on leaves, which will be knocked off and will fall into the water, and will be eagerly snapped up by the archerfish. Archerfish will also leap from the water to grab insects if the insects are very close to the water's surface. They are peaceful towards other species and similar-sized members of their own species, but will act dominant towards archerfish that are smaller than themselves, so get a group of similarly sized archerfish to avoid problems springing up. They can be fed on frozen bloodworm, crickets and mealworms. They are best kept in brackish paludaria with terrestial plants growing down the edges, so live insects such as crickets can be placed on the plants and the archerfish can shoot them down and therefore exhibit their natural behaviour. They like an SG of around 1.005 up to 1.023 and are very tolerant of SG. They are best kept in high temperatures of between 26 and 29 degrees celcius.

Dragon/Violet gobies - Gobioides brousonnetti is a menacing looking goby which is really harmless to nearly all fish - very small fish such as bumblebee gobies and guppies included. It likes a low SG of between 1.003 and 1.010 and likes to eat small invertebrates such as live daphnia, bloodworm and brine shrimp - their dietary habits are virtually the same as the bumblebee goby. They are compatible with virtually all the brackish fish mentioned so far. They grow up to 50cm or so in home aquaria, but are very thin fish that do not produce much waste for their size, so can be kept in a smaller tank than generally recommended for that size. Nevertheless, a tank in excess of 260L is a good idea.

Figure-8 and Green-Spotted Pufferfish - Tetraodon biocellatus and Tetraodon nigroviridis are two popular brackish pufferfish. The Figure-8 grows to around 12cm - the Green spotted to around 15cm. The Figure-8 likes an SG of 1.005 to 1.010, and the Green spotted lives an SG of 1.010 to 1.025. They are generally incompatible with almost every fish already listed, but the Figure-8 can be kept with bumblebee gobies if you wish. Both are territorial. Feed a meaty diet which includes frozen bloodworms. They also enjoy a treat of snails - a good idea is to breed Physa or a similar pest snail in another tank (not malaysian trumpets as these have very hard shells that can damage puffers who try to eat them) and feed these to the puffers regularly. The Fig-8 is best suited to tanks above 90L, and the green-spotted is best suited to tanks above 150L.

Other Brackish Fish - The world of brackish fish doesn't end here. I've only stated some of the most common species - there are far more wierd and wonderful species out there. If you are interested, look up halfbeaks, freshwater moray eels, freshwater pipefish, blackchin tilapia and flounders.


"Thanks for the info, bye!" I hope you enjoyed this article and please feel free to comment on it here. I hope I can encourage a few more people to start keeping brackish aquaria, as they really are fantastic and definitely worth a try, and deserve more popularity.

Photo Credits - A big thank you to both PFK and Angus1 for supplying photos.
Last edited by fishnoob on Wed Feb 17, 2010 11:50 am, edited 2 times in total.

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Postby mudcow304 » Fri Oct 16, 2009 5:21 pm

Great article, thanks. I am going to look at finding some Bumblebee gobies when I get back to the UK now! Sound like good tank mates for my fig 8's!

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Postby fishnoob » Sat Oct 17, 2009 7:18 pm

I'm really glad you enjoyed it, bumblebee gobies are great fish.

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