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Related FAQs: Glassfishes

Related Articles: Glassfishes: Family Ambassidae By Neale Monks,  Seems Fishy To Me:  The Painted Glassfish by Spencer Glass, Brackish Water Fishes

Seeing it through with glassfish;

 How to succeed with these misunderstood fish


© Neale Monks


Glassfish are a regular fixture in tropical fish stores, though often not for the right reasons. For many years they have been almost always imported as 'disco fish', with fluorescent pains injected into their bodies to create brightly coloured fish that easy to sell to inexperienced fishkeepers. However pretty these disco fish might be, the process of colouring them is known to harm their health as well as being a cruel and unnecessary. In particular, dyed glassfish are significantly more likely to contract lymphocystis than undyed fish.

Since 1996, Practical Fishkeeping has encouraged retailers not to stock these dyed fish, and disco fish are now far less frequently offered for sale than before. A knock-on effect has been that glassfish have slipped off the radar as far as many aquarists are concerned, and finding them can sometimes be tricky. Undyed glassfish have a subtle beauty, and they are easily overlooked when kept with brightly coloured, showier fish like fancy livebearers and neon tetras. This is a real shame, because glassfish are definitely nice fish with lots to offer the aquarist looking for something peaceful, easy to keep, and just that bit different.

The not-so-common glassfish

No fewer than three species are imported as common, or Indian, glassfish, and in general, no attempt is made by the retailers to separate them. Fortunately for the aquarist, all require much the same conditions to do well. Really the only difference between them is size: at 3 cm when fully grown, the smallest species, Parambassis lala, being less than half the size of the largest, Parambassis ranga. The third species, Parambassis siamensis, is somewhere between the two, averaging at between 5 to 6 cm in length.

Besides being muddled up by importers and retailers, these glassfish have also laboured under a variety of scientific names. Older books will consign all of them to the genus Chanda, and many aquarists still refer to them as such. More recently, they were moved to another genus, Ambassis, and this name remains common in aquarium books. Finally, some of the glassfish were divided up between two new genera, Pseudambassis and Parambassis. The situation is still far from resolved, but the three species of interest here are currently all placed in the genus Parambassis. Recent aquarium books, as well as magazines and web sites, are most likely to describe these fish under this name.

As if the fact that you could have any one of three, difficult to tell apart species of glassfish in your tank wasn't enough, things get even more complicated when it comes to settling on their ideal water conditions. Traditionally these fish were viewed as brackish water fish, and most books will suggest adding a certain amount of salt to an aquarium containing glassfish. However, collectors insist that these fish are found primarily in fresh water habitats, sometimes even soft and acidic ones.

Glassfish have a reputation for being delicate and tricky to keep, is this because brackish water is harmful to them? Most likely not, since Parambassis lala and Parambassis ranga at least are known to occur in brackish water, albeit rarely. Of the three, only Parambassis siamensis is entirely restricted to freshwater. However, adding too much salt may well stress them over the long term, and these fish certainly don't need strongly brackish conditions like scats or monos. A specific gravity of 1.005 or less is probably safe, and means that these fish could be mixed with bumblebee gobies, pipefish, and other fish that do well in slightly brackish conditions. However, the ideal water conditions are much more like those of other South East Asian freshwater fish: a neutral pH, not too hard, a steady but not overbearing water current, and plenty of oxygen.

Although not fussy about water chemistry, glassfish can be awkward when it comes to feeding. They rarely, if ever, accept flake foods, and even some frozen foods are rejected. My glassfish don't show any interest in frozen bloodworms or mosquito larvae, though they enjoy both of these as live food. Frozen lobster eggs, by contrast, are readily accepted, and make an inexpensive and convenient staple food. Frozen lobster eggs are sometimes difficult to find -- look for them in stores specialising in marine invertebrates, since they're used primarily to feed things like corals and giant clams. Each egg is tiny, but they're rich in fat and protein, and the glassfish seem to go wild for them, darting about, snapping up the eggs.

Oddball glassfish

A newcomer to the hobby is the hump-head glassfish, Parambassis pulcinella. Only discovered in 2003, it has already become something of a staple, and while expensive, is relatively easy to obtain. A classic oddball, this fish not only retains the silvery transparency of the smaller glassfish species, but also sports a spectacular nuchal hump. Males have more strongly developed humps than females, but both have them, and by any standards, these are extraordinary fish. Parambassis pulcinella is a schooling fish, and given that this species grows to around 20 cm, it is obviously best suited to a large aquarium. Not much is known about the health of this fish in captivity, but since the fish normally inhabits fast flowing waters, good filtration and plenty of oxygen are probably crucial to long-term health.

In terms of social behaviour, Parambassis pulcinella is a bit problematic. As with many schooling fish, there is a definite pecking order within the group, and if too few are kept, dominant specimens will harass weaker individuals. You probably want to keep at least six specimens, and ideally ten or more. If you only have the option of keeping three or four specimens, the safest approach is to keep just a single male in the tank, on the assumption that the most aggressive fish within a school tend to be the males.

Another giant glassfish is Parambassis wolffii. Like Parambassis pulcinella, Parambassis wolffii is an inhabitant of fresh, not brackish, water and is very widely distributed in slow moving rivers throughout South East Asia. An adult Parambassis wolffii is an impressive fish despite not being particularly transparent, with sturdy, spiny fins and a rather menacing face! These fish probably have most appeal to those with an interest in oddball predators, which these fish most definitely are. At an adult length of 20 cm, it can easily swallow up fish as large as platies and small barbs. On the other hand, it is completely peaceful with gouramis, catfish, and barbs of comparable size. 

Many books suggest that in an aquarium Parambassis wolffii does not grow any bigger than the 'dwarf' species like Parambassis ranga. This appears to be the result of confusion over which species was actually imported, with Parambassis siamensis often being sold as Parambassis wolffii. Recent imports of Parambassis wolffii have brought them in at around 10 cm in length, and it is probably safe to say that if looked after well these fish will continue to grow. In other words, this species shouldn't be bought on the hope that it will stay small if kept in a small aquarium.

By far the most infrequently imported glassfish, though many would say it is also the most beautiful is Gymnochanda filamentosa. This fish is an inhabitant of acidic, blackwater streams similar to those aquarists associate with discus, though it does tolerate hard or slightly brackish water surprisingly well. Nonetheless, this fish does best when kept in a dark, thickly planted tank alongside neons, cardinals, and other small, blackwater fish. While this fish resembles Parambassis lala, the males are distinguished by tremendously elongated dorsal and anal fin rays. Of all the glassfish, this species is generally considered the most delicate, and it is best left to advanced aquarists.

Glassfish in the aquarium

Keeping glassfish generally presents no problems once the fish are settled in and feeding properly. The main problem is that many fish may not have eaten much over the weeks that they have been on display in the tropical fish store. Since glassfish usually refuse flake or dried foods, if they have not been regularly provided with live or frozen foods, they can quickly become weak and disease prone. Ask the retailer what the glassfish have been fed on: if the answer is flake food, you can safely assume that the fish will be underweight and will need to be looked after especially well once you bring them home.

They are not particularly disease prone, though white spot can be a problem. Some glassfish, most notably Gymnochanda filamentosa, do not have any scales on their bodies, and are in fact very sensitive to skin parasites of all types. Fortunately, glassfish respond well to commercial white spot treatments. Glassfish can also be susceptible to fungal infections as well, and keeping them in slightly brackish water can help to prevent this. However, adding salt is not essential, and in the case of species that are strictly confined to fresh water, such as Gymnochanda filamentosa and Parambassis pulcinella, keeping the fish in brackish water over the long term will probably do more harm than good.

Glassfish are generally not aggressive fish, and the smaller species especially prefer to be kept with quiet tankmates. Persistently aggressive species like the larger cichlids, pufferfish, and some of the sharks and loaches would make bad choices, even for the larger species of glassfish. On the other hand, the small species in particular get along very well with small community fish, and since they are fast moving midwater fish, they even manage to keep out of the way of territorial dwarf cichlids like Microgeophagus ramirezi and Pelviachromis pulcher as well. In short, glassfish are ideal fish for the peaceful community tank, much misunderstood over the years, but finally beginning to be truly appreciated by aquarists looking for something a bit different.

 Information boxes 

Parambassis lala


Origin:                           India to Burma, in slow moving waters.

Size:                              To 3 cm.

Identification:                 Small, deep-bodied, amber tinted fish. There are three vertical black bars on the flanks, and the dorsal and anal fins of the males have electric blue edges.

Water requirements:    Neutral freshwater preferred, can adapt to slightly brackish conditions.

Food:                             Small live foods such as Daphnia and brine shrimp; will also take some frozen foods such as lobster eggs.

Social behaviour:          Peaceful schooling fish.

Breeding:                      Unknown.


Parambassis ranga


Origin:                           From Pakistan to Malaysia, in sluggish and standing waters.

Size:                              To 8 cm.

Identification:                 Small, highly transparent species. Similar in shape to Parambassis lala, but instead of vertical bands on the flanks there is a single dark patch behind the eye.

Water requirements:    Neutral freshwater preferred, can adapt to slightly brackish conditions.

Food:                             Enjoys frozen lobster eggs, as well as live Daphnia, bloodworms, mosquito larvae, and brine shrimp.

Social behaviour:          Peaceful schooling fish.

Breeding:                      Unknown.


Parambassis siamensis


Origin:                           Thailand, Malaysia, and Java.

Size:                              To 6 cm.

Identification:                 Small, highly transparent species. Similar to Parambassis ranga, but lacking the dark spot behind the eye, and not so deep bodied. This species is the one most often dyed and sold as disco fish.

Water requirements:    Neutral freshwater.

Food:                             Small live foods such as bloodworms, Daphnia, and brine shrimp; will also take some frozen foods such as lobster eggs.

Social behaviour:          Peaceful schooling fish.

Breeding:                      Unknown.


Parambassis wolffii


Origin:                           Widespread throughout South East Asia

Size:                              Up to 20 cm, usually smaller in captivity.

Identification:                 Large, silvery species similar in shape to Parambassis ranga. The dorsal, pelvic, and anal fins have very stout spines, and the dorsal and pelvic fins bear distinctive dark patches. Juveniles are more transparent than adults, and can easily be confused with other species of Parambassis.

Water requirements:    Neutral freshwater.

Food:                             Primarily live and frozen foods such as brine shrimp, bloodworms, and Daphnia. Also eats small fish in the wild, so should not be trusted with very small tankmates.

Social behaviour:          Peaceful schooling fish.

Breeding:                      Unknown.


Parambassis pulcinella


Origin:                           Thailand/Burma border, in fast flowing waters.

Size:                              Up to 10 cm.

Identification:                 Large, transparent species with an unmistakeable tall but thin hump on the forehead. This structure is most highly developed in the males.

Water requirements:    Neutral freshwater.

Food:                             Primarily live and frozen foods such as brine shrimp, bloodworms, and Daphnia. Also eats small fish in the wild, so should not be trusted with very small tankmates.

Social behaviour:          These fish can be aggressive towards one another when not kept in sufficient numbers.

Breeding:                      Unknown.


Gymnochanda filamentosa


Origin:                           Malaysia, primarily from blackwater streams.

Size:                              Less than 4 cm.

Identification:                 Small, transparent fish otherwise similar to Parambassis ranga but lacking the dark spot behind the eye. May have an amber or greenish tint. Males have greatly extended dorsal and anal fin rays edged with electric blue.

Water requirements:    Soft, acidic freshwater, preferably filtered through peat.

Food:                             Small live foods.

Social behaviour:          Very peaceful, but shy and must be kept in a fair sized school.

Breeding:                      Egg scatterer, the fry require tiny live foods (infusorians).

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