Parosphromenus nagyi



Known only from a portion of Peninsular Malaysia’s eastern coast.

Type locality is ‘Asian highway Route No. 18, 16 kilometers south of Kuantan, Malaysia’, but a number of populations have been discovered since with known distribution extending southwards from Cherating near Cukai, Terrengganu state, as far as Nenasi in neighbouring Pahang state.

Localities in aquaria include ‘Cherating’, ‘Kuantan’, ‘Tasik Chini’ and ‘Pekan Nenasi’ and some exhibit minor differences in colour pattern (see ‘Notes’).

Based on some other locality details we’ve seen quoted, e.g. ‘Mersing’, ‘Kluang’, ‘Ulu Tiram’, this species may be more widely distributed than is normally reported, though this remains to be confirmed.

In at least one habitat close to Kota Tinggi in Johor state it supposedly occurs alongside or replaced the congener P. alrfedi although doubts persist as to the precise locality where the P. nagyi-type fish were collected.

Some reports suggest they were actually collected near Jemaluang in Mersing district, northern Johor and therefore much closer to the known range of P. nagyi.

Some of the fish in our images were apparently collected in the vicinity of Ulu Tiram, Johor state, significantly further south, and this in particular appears to warrant further investigation since they are very similar to the form from Kuantan.


A stenotypic inhabitant of peat swamp forests and associated blackwater streams.

In unaltered habitats the dense canopy of branches above means very little light penetrates the surface of such environments, and riparian vegetation also tends to grow thickly.

The water is typically stained darkly with humic acids and other chemicals released by decaying organic materials, the dissolved mineral content generally negligible and pH as low as 3.0 or 4.0.

A great deal of its original habitat has been lost via deforestation and other human alterations and it’s considered in danger of extinction.

In the majority of cases it now survives only in remnants of heavily-modified peat swamp habitats such as irrigation ditches and roadside canals.

Maximum Standard Length

30 – 35 mm.

Aquarium Size

An aquarium with base dimensions of 20-40cm or equivalent is sufficient for a pair.


Can be maintained in a fully-decorated aquarium although many breeders prefer not to use a substrate for ease of maintenance.

Driftwood roots and branches can be used and placed such a way that a few shady spots are formed, and clay plant pots, lengths of piping or even plastic camera-film containers can be included to provide further shelter and potential spawning sites.

The addition of dried leaf litter further emphasises the natural feel and as well as offering additional cover for the fish brings with it the growth of microbe colonies as decomposition occurs.

These can provide a valuable secondary food source for fry and the tannins and other chemicals released by the decaying leaves are also considered beneficial for fishes from blackwater environments. Alder cones may also be used for the latter purpose.

Like others in the genus this species does best under fairly dim lighting. You can add aquatic plant species that can survive under such conditions such as Microsorum, Taxiphyllum or Cryptocoryne spp., while floating vegetation, especially Ceratopteris spp., is also useful.

Filtration need not be too strong, with an air-powered sponge filter or similar adequate, and since this species tends to be maintained in pairs (see ‘Behaviour and Compatibility’) a filter may not be required at all provided the fish are not overfed and maintenance is stringent.

The latter must include small weekly water changes of 5-10 % aquarium volume with irregular or larger changes not recommended.

All Parosphromenus spp. require acidic conditions with negligible carbonate hardness and very low general hardness so a reverse osmosis unit or other method of obtaining soft water may need to be employed, and this can be further acidified using phosphoric acid or similar if necessary.

There is no need to use natural peat, the collection of which is both unsustainable and environmentally-destructive.

It goes without saying that these are fishes are sensitive to fluctuating organic wastes and should never be introduced to biologically-immature aquaria.

Water Conditions

Temperature22 – 28 °C

pH3.0 – 6.5

Hardness18 – 72 ppm