Golden Orfe (Idusidus)
This fish is lively and provides a lot of interest in the pond. If kept as a single fish or in a single pair it is shy and rarely seen, but in a shoal it is much more confident, moving quickly and darting out in the open areas of water, and rising to take food from the surface. It is a small hardy fish with a pale golden colour that fades to silver as it nears the dorsal curve, the fins retaining a stronger colour; a silver variety is also available.
The Golden Orfe is long and slender, reaching 30cm (12in) in length. It is an excellent scavenger, removing insects and mosquito larvae from plants and from the water surface. It is best kept in a spacious pond where it can have a good length to swim in; it has been known to jump right out of small ponds. During the winter months it is less active and keeps away from the surface, preferring to lie dormant near the pond bottom.
Golden Rudd (Scardinius erythrophthalmus)
This very attractive fish has a silvery colour with a golden hue. The scales are large, rough and distinct. The eyes and fins are red, and the pectoral, pelvic and anal fins are darker than the dorsal fin. It is often confused with the Roach (Rutilus rutilus), but is distinguishable because its dorsal fin starts well back on the spine, between the anal and pelvic fins.
The Golden Rudd will grow to 45cm (18in) in length, and may reach 2kg (4lb 6oz) in weight. It feeds on worms and ant eggs as well as aquatic vegetation. It is found wild in slow-running rivers and lakes in most parts of Europe. The Golden Rudd lays eggs among weeds, and they hatch in five to eight days. It is quite like the Golden Orfe, of a better shape but not so bright in colour. This hardy species thrives in the open pond, where it lives well with other fishes.
Green Tench (Tinea tinea)
This very hardy fish will live a long time out of water. It grows well and increases quickly in still water, which it prefers to running water. The skin is slimy and this is reputed to cure various diseases on other fishes in the pond. Its natural food consists of insects, worms and young shoots of water vegetation. It will increase quickly where the conditions are right, and two males should be provided for each female; the sexes can be distinguished by the size of the pelvic fin, which is larger in the male. The mouth has a barbel on each side. This fish is dark green in colour, with pink lips and very dark green fins. When mature it may reach a length of 45cm (18in), and weigh up to 2.5kg (5lb 8oz). These fishes are excellent scavengers as they always eat off the bottom of the pond. They are often found in rivers, ponds and sand pits.
Golden Tench (Tinea tinea)
The Golden Tench, a variety of the Green Tench, is an excellent fish to add to the pond. It is golden with a yellow hue. The mouth is toothless with a small barbel at each side, blunt and leathery. The fine scales are covered with a mucus that gives it a slimy feel. The dorsal and anal fins are without bony rays, and the shape of the caudal fin varies with the age of the fish: concave when young, straight as it matures and convex when old. This variety will increase rapidly if two males (which have larger pelvic fins than the female) are provided to each female. The Golden Tench enjoys insects and worms, and is a scavenger that invariably eats off the pond bottom. When the fish is fully grown it can reach almost 45cm (18in) and up to 2.5kg (5lb 8oz).
Minnow (Phoxinus phoxinus)
These small fishes are found in the wild in many streams, ponds and rivers, and they readily settle into pond life. They prefer to live in shoals, where they are very active and give plenty of movement to the water. They live for quite a long time, and individuals have been known to survive for 12 years in a pond. In spring the male minnow changes colour from its original olive-brown to a green flushed with red. The female will spawn on gravel, and the eggs hatch in about ten days.
With a change in the surroundings Minnows will change colour, turning lighter or darker according to the background. The dorsal fin is placed well back, over the space between the pectoral and anal fins. The tail is forked, with large spots at the base. The fish has a total length of some 7.5cm (3in). Minnows are hardy, and bold in taking food from larger fishes; they enjoy flies, meat and worms.
For that extra challenge
There are a number of other fish that can be kept in a coldwater pond, but are less decorative or require more specialized treatment than the Common Goldfish. These are probably best reserved for the more enthusiastic fishkeeper when the more common fishes start to become less interesting.
The various Carps such as the Crucian Carp (Carassius carassius), the Leather and Mirror Carps (Cyprinus carpio), and the Prussian Carp (Carassius auratus gibelio) are likely to be less noticeable in the outdoor pond, but some of these are suitable for food-farming. The most popular of the food fishes are the Trouts, either the Rainbow Trout (Salmo gairdneri) or the Common Trout (Salmo trutta) but they do need a higher oxygen level in the water. This can be achieved by using a more powerful pump to move a larger quantity of water. Also, as the oxygen requirements are so high, less Trout can be accommodated in the pond compared with other species.
Some ‘tropical’ freshwater fishes can be kept successfully in outdoor ponds – at least during the summer months in temperate climates. These include Japanese Ricefish (Oryzias latipes) and White Cloud Mountain Minnow (Tanichthys albonubes).