In general the brackish water species we see on offer to the aquarium hobby are potentially specialist fish, and some knowledge needs to be gained about them before making a purchase. The fact is that some of them will be happier in full strength sea water as their preferred environment. Others need just a certain amount of salinity to satisfy their water chemistry needs. Only a few will easily acclimatise to completely freshwater. So it is recommended very few of the brackish water species offered should be considered for a freshwater aquarium, and care must be taken when attempting to mix different species in the same brackish aquarium, as many of them are quarrelsome fish with both their own kind and other species.
The Malayan Angelfish (monodactylus argenteus) is one of the easiest brackish water fish to acclimatise to entirely freshwater conditions, given the pH and other factors are within tolerable margins. However, we recommend it should always be kept in either the brackish water or marine aquarium. It is a very attractive fish and as such is sometimes bought without enough being known about its habits. It is not suitable for inclusion in a community of small fish, as it can become quite ebullient with age, and its dietary requirements for the best results are somewhat special.
Scats are truly a marine fish, but will live quite happily in brackish (part-salt) water, and just a few will successfully adapt into completely fresh water. They tend to be somewhat “picky” and may be quite harassing of their own kind, especially if the diet is lacking in variety and the correct type. There are two colour forms of the Tiger Scat (Scatophagus argus) – the red form pictured, and a green metallic form.
There are many other species of freshwater fish we could mention in this section, but within the scope and space of this site we have selected two interesting species. Both are specialist fish, intended for the hobbyist prepared to devote the space and time required for the keeping of such exotic species.
Freshwater Stingrays from South America are regularly imported for the aquarium hobby now. These beautifully marked and spectacular creatures are related to the marine sharks and rays, bearing their young alive in the same way. They need plenty of space, judicious feeding, and excellent water quality, for success, and are most certainly not for the beginner!
This species of arowana is found in South America, although there are Asian species too. The eventual mature size of this fish is big, and the aquarium needs to be large and well covered to accommodate even one specimen. When they are still juvenile or sub-adult they may be kept in a group, but as they grow towards adulthood they can become very aggressive towards one another, and indulge in fighting with a view to killing off the competitors and leaving one dominant fish. They are accomplished jumpers!