I have now maintained four species of halfbeaks, the common "wrestling halfbeak", Dermogenys pusillus, its more prolific cousin, Dennogenys montanus, the larger and more colorful Celebes halfbeak, Nomorhamphus liemi liemi, and its magnificent cousin, Nomorhamphus ebrardti. These haffbeaks, and other species of the three genera Dermogenys, Hemirhamphus, and Nomorhamphus inhabit the shallows of tropical Asian waters on such islands and peninsula as Indonesia, Sumatra, Malaysia, Java, Singapore, and Thailand. By virtue of a distinctive physiognomy, they inhabit the upper reaches of waters as warm as 95F and subsist on a diet of such live floating foods as mosquito larvae. In the more confined environment of the aquarium, halfbeaks tend to occupy the upper and middle strata and do well on floating flake food and all live foods that do not sink quickly to the bottom. They are not fussy as to purity of water, pH or hardness, with one massive exception I will detail later. Halfbeaks are not fussy in diet nor overly sensitive to overcrowding or marginally polluted water.
Dermogenys pusillus is a species well known to fishkeepers here in Minnesota and has been written up quite accurately in an earlier Aqua News by Lenny Ancheta. Of all the halfbeaks I have kept, D. pusillus is the most fond of the aquarium surface. I obtained my colony from Lenny and enjoyed success in propagating them by isolating gravid females in well planted aquaria with very low water, then watching daily for fry that resemble little dark squiggles in the floating duckweed. The female is removed immediately and fry grow rapidly on powdered dry food supplemented with newly-hatched brine shrimp. Every four weeks, as regular as clockwork, a mature female delivers 15-30 new fry. The American Livebearer Association brood record is 38. Only Randy Carey has exceeded that figure and now reigns as the fertility czar of the wrestling halfbeak.
Dermogenys montanus is a similar species but more active, more prolific and more comfortable in mid-range levels of the aquarium. I obtained my adult pair from Jim Robinson of Mississauga, Ontario, and maintained them in a long twenty gallon aquarium at temperatures averaging 77" F., with neutral and rather soft water. The diet was of dry foods and brine shrimp. Broods every four weeks ran between twenty and 35, well short of the A.L.A. record of 49. D. montanus closely resemble D. pusillus but seems more robust with more presence in the aquarium.
The Celebes halhbeak, Nomorhamphus liemi liemi, is also quite well known to Minnesota aquarists. I obtained a nice colony from Lenny Ancheta but experienced problems with cannibalism and water chemistry until I was reduced to three gravid females who delivered more than fifty fry within two days. I then donated the females and experienced minimal difficulty raising the fry for four months until a disaster, that I shall relate shortly, struck. Like other Nomorhamphus, the Celebes halfbeak is a much larger and robust species than the various Dennogenys and is distinguished by attractive red and black markings on body and finnage.
Nomorhamphus liemi liemi
My favorite halfbeak has been Nomorhamphus ebrardti. It is less gaudy in appearance than N. Liemi liemi but is attractive in its own right with a burnished body and reddish fins. It has much more presence than the previously mentioned species. I again obtained this pair from Jim Robinson. A day after reaching Duluth, my female yielded a dozen healthy fry. The next spawn, a month later, consisted of a single sickly fry, perhaps because the male leapt the partition and dined royally. Four weeks later the female yielded thirty strong fry, so, with a colony approaching maturity, I gave the adults to Lenny Ancheta. Subsequently, disaster befell my colony and other populations in the state.
I have found all species of halfbeaks hardy, with one significant exception -- they seem to possess a remarkably low tolerance for quick alterations in water chemistry. Mine have tolerated ranges in pH from 6.2 to 7.8 and somewhat polluted water with no signs of distress. I have lost entire populations of D. montanus, N. ebrardti, and N. liemi liemi, however, following water changes with rather small adjustments in pH. In every instance, the symptoms have been similar. The fishes would shimmy near the top with fungus erupting from open body sores in the dorsal area, then succumb one by one despite a number of different remedies and medications. Without fail, whole populations were lost. In some instances, water changes were as little as twenty percent, resulting in pH swings to alkaline of .4 or less.
This leads me to a suggestion. When next I try to maintain any halfbeaks, I will supplement my regular filtration with a corner box filter containing dolomite or crushed coral to maintain constancy of pH -- the alkalinity is not necessary but the stability of pH seems to be. Instead of substantive water changes, I will change a gallon or two every two or three days, trickled in by the drip method. This way I believe these interesting species can be maintained with little difficulty.