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By Neale Monks
Glassfishes are small, perch-like fishes from Southern Asia, Australia, and neighboring islands including New Guinea. Their common name comes from their remarkable transparency, something that makes the large species in particular very attractive aquarium fish. Only a handful of species are regularly traded, but in recent years the diversity of Glassfishes offered to the aquarist has steadily risen, with the hump-head Glassfish from Burma (Myanmar) being now quite widely sold. Do They Need Salt? One of the most widely held myths in the hobby is that Glassfish need brackish water. It is certainly true that there are brackish water Glassfish, and even a few that live in the sea, but none of these are routinely traded as aquarium fish. Most of the species sold to aquarists come from freshwater streams and ditches, while a few come from rivers and blackwater streams. By default, therefore, any Glassfish offered for sale in a tropical fish shop should be thought of simply as a freshwater species and housed accordingly. Dyed Fish For many years, Glassfish have been widely sold with fluorescent dyes injected into their bodies. These so-called "Disco Fish" or "Painted Glassfish" often sell well, being particularly attractive to inexperienced aquarists after something cheap and colourful. At best, the dye simply fades away, but at worse, it opens the fish up to a variety of diseases. Lymphocystis is especially common on dyed glassfish. Regardless of the health risks, the ethics of injecting fish with colored paint is dubious, and the fish are likely stressed by the processes and in significant pain afterwards. These fish aren't tattooed: the paint is injected into the muscle, not the skin. Think about the last time you had an intramuscular injection! Not much fun at all... Common and Not-So-Common Glassfish Ambassis agrammus is sold as the Highfin Glassfish or Olive Glassfish. It comes from Australia and New Guinea. Superficially similar to the common Glassfish, Parambassis ranga, it has a noticeably taller dorsal fin and a slight greenish tint to the body. This is a strictly freshwater species that does best in soft to moderately hard, slightly acidic to neutral water. Grows up to 7.5 cm (2.75 inches) in length. It is a peaceful, schooling species that naturally inhabits rainforest streams and swamps, and consequently does best in thickly planted aquaria. Known to be prone to Lymphocystis if kept in suboptimal conditions. Gymnochanda filamentosa from Malaysia and Indonesia is known as the Threadfin Glassfish and is one of the most beautiful of all the Glassfish. It is a small fish, about 4 cm (1.75 inches) in length but the males have dramatically elongated rays to their anal and dorsal fins. The edges of the anal, dorsal, and tail fins are electric blue. These fish had been absent from the hobby for many years, but are no starting to appear again with some regularity. They are lovely animals, but they are also more delicate that the other Glassfish and should either be kept alone or with small, very peaceful tankmates. Older aquarium books often suggest that these fish need brackish water; they actually come from blackwater habitats of the type enjoyed by Rasboras and Chocolate Gouramis, and so need soft, acid water with pH around 6.0 and a hardness below 10-degrees GH. Parambassis lala is often mentioned in aquarium books but is actually quite rare in the hobby. From India, Bangladesh, and Burma. A delightful species; it has a yellow-gold tint, with the males also having a brilliant blue edge to the dorsal and anal fins. These fish get to around 3 cm (1.5 inches) and can be kept in the same way as the common Glassfish Parambassis ranga with which they are sometimes confused. Normally found in streams and ditches, and best kept in soft, slightly acidic water, though will tolerate hard, more alkaline water well. Parambassis gulliveri is known as the Giant Glassfish on account of its large adult size, around 24 cm (9.5 inches). It is found in Australia and New Guinea and only rarely exported to other parts of the world. Nonetheless, it is a spectacular fish for the connoisseur. Instead of being transparent or silvery like most of the other Glassfish, it has dark regions around the scales on the top half of the body producing a dramatic net-like pattern. The pelvic and anal fins are yellow, and the tail fin mid-grey. Like all Glassfish, this is a predator, but being such a big fish, it will eat small fish as well as insects and crustaceans. It is a freshwater species that normally inhabits big river systems, so a tank with strong water current, good filtration, and lots of oxygen will be required. Water chemistry parameters relatively unimportant, but avoid extremes. Large Glassfish species are often quite pushy and aggressive, and this species is no exception. Keep with sturdy tankmates such as Catfish and Barbs, and to avoid fights between rival makes, keep in groups of five or more. Parambassis pulcinella is the remarkable Humphead Glassfish from Burma and parts of Thailand. A stunning fish, even at their full size they are still surprisingly transparent. Both sexes have humps between the head and the base of the dorsal fin, though the humps of males are larger. Male fish can be aggressive towards one another, so in small groups keep just a single male. Grows to around 10 cm (4 inches) in length and being predatory, should not be kept with very much smaller tankmates. Maintenance of this freshwater species is similar to Parambassis gulliveri, in particular the need for well-oxygenated, clean water. Neutral, moderately hard water appears to be the ideal as far as water chemistry goes. This is a new fish as far as science goes, only discovered in 2003, and when offered as an aquarium fish, it is usually quite expensive.
Parambassis ranga is the ‘common’ Glassfish, though it is frequently confused with the nearly identical Parambassis siamensis. Parambassis ranga is found right across South and Southeast Asia, from India to Malaysia. It is transparent with a slightly grayish tint when mature, and largely unmarked except for a small grey patch behind the gill covers and, in the case of males in breeding condition, blue edges to the anal and dorsal fins and sometimes bluish markings on the pelvic fins. While a good community fish in terms of being harmless towards anything bigger than livebearer fry, these fish are pushy and fairly aggressive towards one another unless kept in very large groups. Despite their reputation for being shy fish, when settled in they will engage in chases and fights all through the day! This species is most commonly found in freshwater streams and ponds, typically in sluggish water, and is only rarely found in brackish water. In aquaria it will adapt to a wide range of water chemistry values, from soft and acidic through to slightly brackish (specific gravity up to 1.005). However, the ideal seems to be soft, slightly acidic water under which conditions the fish is robust, resistant to disease, and more willing to spawn. Known to be prone to Lymphocystis when kept in suboptimal conditions. Parambassis siamensis is another commonly traded Glassfish and is said to be the species most frequently injected with fluorescent dyes and sold as ‘Disco Fish’ or ‘Painted Glassfish’. It occurs across Southeast Asia, from Thailand to Indonesia. It is very similar to Parambassis ranga in shape and color, but is a little smaller, only getting to about 6 cm (2.5 inches) in length. This species sometimes lacks the grey patch behind the gill covers. For most practical purposes, the aquarist can treat the two species as identical in terms of care and social behaviour, and it is similarly prone to Lymphocystis when kept improperly. Parambassis wolffii is a large freshwater species that is only infrequently offered for sale. It is widely distributes across Southeast Asia. Juveniles are very transparent and can easily be mistaken for Parambassis ranga. Adults have a distinctly angular jaw-line and a steely-grey tint, and are of course very much larger, up to 20 cm (8 inches) in size. They are peaceful though highly predatory, and like other Glassfish, individual fish can be a bit pushy towards one another when kept in small groups. Normally found in sluggish rather than fast-flowing rivers, it is adaptable in terms of water chemistry provided extremes are avoided. As with so many other glassfish, this species is known to be prone to Lymphocystis when kept under suboptimal conditions. Aquarium Requirements Broadly speaking, the smaller species inhabit sluggish, thickly vegetated waters, while the larger species common from rivers where they inhabit open water. Aquarium conditions should reflect these preferences. Neutral, moderately hard water will suit most species well, while some do seem to prefer more acidic conditions. None needs brackish water, though the common glassfish can be adapted to slightly brackish water if required. Glassfish are generally quite robust, but they are sensitive to low oxygen concentrations, and with the larger species in particular, additional aeration is likely to be useful. Social Behaviour Glassfish have a reputation for being shy, and this is certainly true when they are held in small tanks in tropical fish shops. However, when settled in, they become very different, and can be compared with robust barbs and tetras in terms of social behaviour. In large groups they will form schools, but when kept in groups of less than a dozen they often become a bit more belligerent towards one another. Fish will snap at one another or engage in short chases, but usually no harm is done. These fish get along very best with peaceful tankmates of similar size. Larger, more aggressive tankmates, such as cichlids, will frighten them, but schooling fish of similar size work very well. Since these are Asian and Australasian fish, Barbs, Rasboras, Rainbowfish, and Halfbeaks are all ideal tankmates. Glassfish are not fin-nippers and can therefore be kept successfully with Gouramis. Feeding A persistent myth among aquarists is that Glassfish only take live food. While they usually do not care much for flake, they will take all kinds of frozen foods with gusto, including bloodworms and krill. Glassfish will also take small pieces of prawn or fish meat. Live foods are enjoyed of course, with the smaller species having a particular fondness for brine shrimp and daphnia while the larger species prefer river shrimps and earthworms. For whatever reason, small Glassfish love lobster eggs! Lobster eggs are sold for use in reef tanks as a dietary supplement for things like corals. Feed only small amounts at a time because if you put too much in, the Glassfish will miss many of them, and all these will do is end up in the substrate or sucked into the filter. Prawn eggs are larger and Glassfish enjoy them even more, but these are not normally sold as aquarium food. Instead, scrape them off unshelled prawns bought from the fishmonger and store them in the freezer. These fat and protein rich little morsels are great for getting newly imported fish back into tip-top condition. When prawn eggs are available will depend on your locality; North Atlantic prawns have eggs only during mid to late spring. Healthcare: Lymphocystis Glassfish are generally robust fish and are not particularly prone to things like whitespot and fungus. Provided they are feeding well and not harassed by their tankmates, they can be thought of as hardy, long-lived fish perfectly suitable for even relatively inexperienced aquarists. However, one particular issue with glassfish is Llymphocystis. This manifests itself as small, off-white nodules on the fins and, less frequently, the mouth and face. It is a viral infection and essentially untreatable, but on the other hand it usually goes away by itself, although this may take months, even years. The causes are not fully established, but environmental conditions are certainly a major factor. Overcrowding, poor diet, and inappropriate water chemistry values are like the major factors that the aquarist needs to consider. Fish that have been dyed also seem to be particularly a risk, presumably because of the trauma of the dyeing process, which is one good reason not to buy these fish. Breeding Glassfish are not commonly bred in aquaria, although the smaller species will at least spawn relatively easily. Clean, slightly warmer than normal water and morning sunshine seem to be the triggering factors. Lowering the salinity, if kept in brackish water, is important as well. Sticky eggs are scattered among bushy plants. Though some scientific authorities say that glassfish guard their young, in aquaria the parents show no interest in the eggs. Indeed, given the predatory nature of glassfish, it is wise to remove the parents before the eggs hatch. The eggs are susceptible to fungus, and appropriate preventative measures will need to be taken. The eggs hatch after about a day. The tricky part is raising the fry, which are very small, and only take live foods. Newly hatched brine shrimp are a bit too big, but infusoria are a bit too small. Cyclops nauplii are one established option. Once the fry grow a little, then regular foods, like newly hatched brine shrimp and then small daphnia, can be used. Glassfish fry form schools, and the food needs to wash past them or they will ignore it.
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