PFK Articles: A fishkeepers guide to glassfish

[AquaticQuotient.com]

Neale Monks explains how to keep the many varieties of glassfish on sale at specialist aquatic shops. Here is an extract of the complete article.

Copyright © Practical Fishkeeping

Glassfish are a regular fixture in tropical fish stores, though often not for the right reasons.

For many years they were almost always imported as 'disco fish', with fluorescent paints injected into their bodies to create brightly coloured fish that appealed to inexperienced fishkeepers.

However pretty these disco fish might be, the process of dyeing is known to harm their health, as well as being 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 fishkeepers are concerned, and finding them can sometimes be tricky.

Which is a pity as undyed glassfish have a subtle beauty that is easily overlooked when kept with brightly coloured, showier fish like fancy livebearers and Neon tetras.


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, all require much the same conditions to do well. The only difference between them is size – at 3cm/11/3" when fully grown, the smallest species, Parambassis lala, is less than half the size of the largest, P. ranga. The third, P. siamensis, is somewhere between the two, averaging 5-6cm/2"-21/4".

Besides being muddled up by importers and retailers, glassfish have laboured under a variety of scientific names. Older books consign all of them to the genus Chanda, and many people still refer to them as such. More recently they were moved to another genus, Ambassis, and this name remains common in literature. 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 all in Parambassis. Thankfully, recent aquarium books, magazines and web sites tend 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 were viewed as brackish fish, and most books suggest adding an amount of salt to their aquarium. However, collectors say these fish are found primarily in freshwater 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 P. lala and P. ranga are found in brackish water, albeit rarely. Of the three, only P. siamensis is entirely restricted to freshwater. Adding too much salt may 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, which 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, and even some frozen foods are rejected.

My glassfish don't show any interest in frozen bloodworm or mosquito larvae, though they enjoy both 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 primarily used to feed 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, P. 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, and by any standards, these are extraordinary fish. P. pulcinella is a schooling fish, and given that this species grows to around 20cm/8", 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, P. 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, 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 P. wolffii. Like P. pulcinella, it is an inhabitant of fresh, not brackish, water and is very widely distributed in slow-moving rivers throughout South-east Asia. An adult P. 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 most definitely are. At an adult length of 20/8"cm, it can easily swallow 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, P. wolffii does not grow any bigger than the 'dwarf' species like P. ranga. This appears to be the result of confusion over which species was actually imported, with P. siamensis often being sold as P. wolffii. Recent imports of P. wolffii have brought them in at around 10cm/4", 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 also the most beautiful, is Gymnochanda filamentosa.

This fish is an inhabitant of acidic, blackwater streams similar to those associated 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 their 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 hobbyists.


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 in the fish shop.

Since glassfish usually refuse flake or dried foods, if they have not been 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 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 whitespot 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. Fortunately, glassfish respond well to commercial whitespot treatments.

Glassfish can be susceptible to fungal infections, and keeping them in slightly brackish water can prevent this. However, adding salt is not essential, and in the case of species that are strictly confined to freshwater, such as G. filamentosa and Parambassis pulcinella, keeping them in brackish water over the long term will probably do more harm than good.

Glassfish are generally not aggressive, and the smaller species prefer to be kept with quiet tankmates. Persistently aggressive species like the larger cichlids, pufferfish and some of the sharks and loaches are bad choices, even for the larger species of glassfish. On the other hand, the small species get along very well with small community fish, and since they are fast-moving midwater fish, they manage to keep out of the way of territorial dwarf cichlids like Microgeophagus ramirezi and Pelvicachromis pulcher.

In short, glassfish are ideal for the peaceful community, much misunderstood over the years, but beginning to be truly appreciated by those looking for something a bit different.

Complete article by Neale Monks here...

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