Native Fish & Invertebrates

Native species of fishes obviously depends on where you live, but among fishkeepers the term is generally used to indicate temperate water species as opposed to the tropical species that make up the bulk of the ornamental fish trade. Brackish water species of goby, blenny, stickleback and flatfish can all make good aquarium inmates provided their basic requirements are met. The main issue is temperature. Temperate water fishes are used to low and moderate temperatures, and prefer a temperature around 15 to 18° C. The following are European species that should do well.

Gobies

The sand goby Pomatoschistus minutus and the estuarine gobyPomatoschistus microps are two hardy European gobies that will do well in aquaria. They can be found in great numbers in estuaries and rock pools from Britain and Scandinavia down to the Mediterranean and Black Sea. Both grow to about 10 cm (4 inches) and are attractively patterned and will readily feed on small frozen foods as well as insect larvae, brine shrimp and similar live foods. They appreciate a soft sandy substrate for burrowing into and being somewhat territorial it is a good idea to provide them with plenty of sea shells or artifical caves like flower pots. A specific gravity of 1.010 and upwards is ideal. Aeration of the water is essential particularly in summer when the temperature may become somewhat higher in an indoor tank than in their natural habitat, but otherwise these are robust and hardy fishes. I have come across these fishes quite commonly mixed with live river shrimps and sticklebacks being sold as fish food. Gobies are often suprisingly good at jumping out of uncovered aquaria.

Blennies

The peacock blenny Salaria pavo is a brackish-water species found along the Atlantic coastline of North Africa through to the Black Sea. It will tolerate freshwater and marine conditions but does best in brackish water. It is a hardy, active predatory fish that will eat most foods and has proven to be easily maintained in aquaria, but it is apt to be aggressive and territorial towards other fish. Like gobies, this fish needs lots of hiding places and a securely covered aquarium.

Two temperate zone blenny species should be mentioned with regard to fishkeeping. One is the shanny, Lipophrys pholis. This rockpool dweller is an excellent aquarium fish, notably for its adaptability and hardiness. It does very well at room temperature, though in summer it will crawl out of the water to cool down on top of any conveniently placed rocks or filters. Although the shanny is undoubtedly able to tolerate short-term changes in salinity given its habitat, it isn’t a brackish water fish and shouldn’t be kept in a brackish water aquarium.

Very occasionally, the freshwater blenny Salaria fluvialitis is seen in tropical fish shops. It is a mountain stream fish that needs cool, well oxygenated water similar to the conditions enjoyed by subtropical danios, loaches and barbs, with which it would mix very well. Although territorial, it is otherwise a good community aquarium fish. That said, it has no place in a brackish water aquarium.

Sticklebacks

Sticklebacks are widely distributed throughout the northern hemisphere. The three-spined stickleback Gasterosteus aculeatus is found in North America, Asia, North Africa and Europe in freshwater, brackish and marine conditions. They have been much studied by biologists in particular because of the ease with which their breeding behaviour can be observed in captivity. Sexually acitve males are very pretty, bright blue or green with shiny eyes and a deep orange or red belly. Females and males outside of breeding condition are a pale yellowy-silver.

Although widely distributed, individual populations appear to be suited to fresh, brackish or marine conditions, and the collector should set up an aquarium for these fish according to where they are collected. Essentially very hardy, though good filtration and well oxygenated water are important. They are distinctly predatory and should be offered frozen or live foods such as bloodworms, brine shrimps and water fleas.

Outside of the breeding season these sticklebacks are gregarious and essentially peaceful towards one another; during the breeding season males are highly territorial. Sticklebacks are best kept alone and tend to mix poorly with other fish species; they will often bully small fish, while larger fish may view them as food.

The nine-spined stickleback Pungitius pungitius is a more cold water species found in Europe, Asia and North America and needs a cool aquarium with excellent filtration and oxygenation. It can be found in fresh waters but is primarily a brackish water and coastal marine fish. The fifteen-spined stickleback Spinachia spinachia is a strictly brackish and marine fish that can be found in rock pools, sea grass meadows and similar habitats where it looks and behaves rather like a pipefish, sneaking up on the small animals it eats. It requires a similar cool, well filtered tank to the nine-spine stickleback.

Flatfish

The common European plaice, Pleuronectes platessus, when small makes a good inmate for a cool-water strongly brackish or marine aquarium. It is hardy, tolerant of room-temperature water, and not at all shy. It will readily accept non-living foods once settled in, even catfish pellets. The European plaice grows quite large though, up to 100 cm (36 inches) in length, and can live for fifty years.

The flounder Platichthys flesus is similar to the plaice but smaller and tolerant of a wide salinity range, wild fish being commonly found in freshwater rivers miles from the sea. Maintenance is similar to the plaice, though this species tends to be a bit shyer and a little more delicate under aquarium conditions.

Invertebrates

Numerous small invertebrates can be added to a native brackish water aquarium, but needless to say the exact species will depend on where you are collecting them. Shore crabs, Carcinus maenas, are extremely hardy even of tropical temperatures and will adapt to any marine or brackish aquarium quickly. Adults will tolerate a range of conditions from normal marine to only slightly brackish (a specific gravity of about 1.004), and will thrive in anything from half to full strength seawater. These crabs do get big, aggressive and predatory though and so usually only small specimens are suitable for aquaria. They are also apt to come out of the water when warm, and will escape from an aquarium if they can.

Much more suitable is the small estuarine mussel crabs of the genus Pinnotheres. These never get bigger than one centimetre (0.4 inches), and only the males are likely to be seen moving about. The females are larger, red in colour, and live inside mussel shells. Small hermit crabs may also be found, and if from brackish water environments, kept in an aquarium easily. As is well known they use old snail shells for protection, and do need a range of successively larger shells to choose from as they grow.

Small shrimps such as the brown shrimp Crangon crangon and the common prawns Palaeomon elegans and Palaemon serratus are also very hardy but likely to be eaten by substantially bigger fishes. They will do fine with the smaller gobies though.