European Bitterling (Rhodeus amarus) Species Profile & Care Guide

European Bitterlings are a prevalent, peaceful, active and hardy coldwater fish that you can keep in both ponds and aquariums. This species can quickly adapt when it comes to water requirements and can handle various temperatures, pH, and general hardiness.

You can keep these fish with various species, including Goldfish and coldwater natives such as Murray River Rainbows. European Bitterlings are not aggressive fish, and they will not nip the fins of other fish.

European Bitterlings have a wide laterally compressed body that displays a beautiful bluish-green iridescent sheen and long rose coloured dorsal and anal fins. The pelvic and pectoral fins are usually white. Their eyes are gold and red and relatively large, and their mouths are slightly up-turned. These fish also display a blue-green stripe along their middle, and their belly is whitish to somewhat reddish.

However, when the males are in the breeding season, they will get a bright orange shine to their bellies, and the fish's fins will change to a bright red colour.

Natural Habitat of the European Bitterling

European Bitterlings are endemic to central and eastern Europe and northern Asia, ranging from the Rhone River basin in France to the Neva River in Russia. However, these fish are not found in Denmark, Scandinavia, or large parts of the United Kingdom.

They inhabit clear, shallow, stony, still, or slow-flowing water in ponds, streams, lakes, canals, rivers, backwaters and oxbows where mussels are present. Their habitats are covered in dense aquatic vegetation, and the substrate usually comprises mud or sand.

European Bitterlings are abundant and expanding in most of their range; however, they are locally threatened due to weed clearing, water pollution, and stocking of predatory fish, leading to a drop in mussels, leading to a decline in this species.

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Diet

European Bitterlings will feed on algae, insects, crustaceans, and organic and inorganic material in the wild. In the aquarium, these fish are not particularly picky and will accept most foods. However, their diet should contain a mixture of dried foods such as flakes, pellets and granules alongside live and frozen foods, like bloodworms, daphnia and brine shrimp.

Breeding the European Bitterling

European Bitterlings reach sexual maturity at around a year old and have a fascinating and unusual breeding method. These fish spawn between April and June. At this time, males will develop an orange belly and reddish fins, while the female produces a long, tubular ovipositor.

The females will insert their ovipositor into the incurrent respiratory siphon of a freshwater mussel or clam and then deposit her eggs in the gill chamber of the mollusc. The female can release anything from 1 to 6 eggs with each spawning. The eggs are then fertilised from sperm ejected by the male then ingested by the mollusc into the gill chamber along with water for respiration.

The eggs will then remain inside the mussels gill cavity for around four weeks, after which the fry emerge fully able to fend for themselves and leave the host.

The breeding periods of fish and mollusc coincide, and the mollusc, in return, throws off its larvae onto the bitterling, where they share part of their development buried in the skin of the fish.

Frquently asked questions about the European Bitterling

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