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General Care for
Brackish Water Fish

Mono argentus

Mono argentus are a common brackish water fish offered for sale.

By Tony Griffitts

What is brackish water?

Brackish water fish are normally found where rivers, streams, and creeks meet the ocean.  These bodies of water could be river deltas, mangrove swamps, bays, and other coastline bodies of water where the saltwater mixes with freshwater runoff from land masses.

List of fish that are commonly sold that live in brackish water:

Molly, Scat, Mono, Spotted Puffer, Figure Eight Puffer, Dragon Goby, Mudskippers, Four-eyed Fish, Bumble Bee Goby, Glassfish, Archer Fish, Black Fin Shark Catfish, Needle-nose Gar, Chromide, Datniode (aka. Siamese Tiger Fish), Freshwater Snowflake Moray Eel.


Water should contain at a minimum, 1 tablespoon of salt per gallon.  Ocean water contains about 8 tablespoons of salt per gallon.  Ideal salt content for most brackish water fish is around 4 tablespoons of salt per gallon.  Salt content can be measured with a hydrometer.  Freshwater measures 1.000, and seawater measures around 1.023 specific gravity.  A salinity of 1.012, equates to about half freshwater and half seawater.  The best salt to use is the synthetic sea salt sold for use in marine aquariums.  Regular aquarium salt can also be used, but it lacks other minerals used to buffer the water so a basic or alkaline pH can be maintained.


70 to 85F           


7.8 to 8.3

Habitat/Proper Aquarium Set up:

Aquarium should have coral or aragonite sand to help maintain a high pH.  The aquarium can be decorated with rocks, caves, and plastic plants if so desired.  Most live aquarium plants cannot tolerate salt levels needed to maintain healthy brackish water fish. 


Most brackish water fish will eat most frozen foods like brine shrimp, bloodworms, mysis shrimp, krill, and plankton.  Most will also eat dry foods.  Live foods like tubifex worms, ghost shrimp, and goldfish can also be offered to many of the species of fish.

Special Note:

Many of the species of brackish water fish can also live in marine aquariums.  Many of the brackish water fish are marine fish (i.e. Monos, Scats, Freshwater Snowflake Moray Eel, Figure 8 Puffer, Spotted Puffer) that will enter freshwater to find food.

Published - 2003

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