Ask the WWM Crew
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One of my early pet-fish industry experiences on moving "back" to the U.S. from overseas (as a military dependent in the late sixties) was a visit to "Worldwide", a freshwater tropical fish wholesaler. Traveling on up with my employer, Don Wolfe, I was immensely fortunate to meet the owner, Bob Holly (whom after these decades is still a friend and still in the trade, working with Steve Lundblad of Dolphin International).
"Big" Bob (I'm little Bob as you might guess), was wondering about in his usual garb, a jump suit, with many pockets filled with capsules of sulfa drugs and the latest antibiotics of the time, administering to his vast collection of Pemco "breeder" flat tanks (no centralized filtration in those days, sigh), when I asked, "Mr. Holly" what's the deal with some of your tanks being covered by screens"? If memory serves, Big Bob explained that this was to prevent jumping by some of the more excitable species. This, along with keeping the lights on 24/7 greatly reduced losses. To emphasize his point Big Bob said, "Listen", as he switched off the lights. Sure as anything it sounded like a sprinkling of large water drops striking cold steel or the beginning of a passing storm on a tin roof in the tropics.
"What was that"? I asked, being a foolish young person then (now a foolish middle-aged person). Big Bob stated, "Mainly the row of upper tanks with all the Chalceus in them". "We keep them high-up to lessen the amount of spooking from folks walking by, and to provide slightly warmer water".
Many years later, here I am relating what I know firsthand and what I can find in the scientific and ornamental aquatics literature to inform and inspire you in the care of this genus.
Chalceus are members of the huge "Tetra" group, the characiform fishes. The Order Characiformes is characterized by "almost always" characteristics: Most have well-developed teeth, and adipose fin is usually present, their bodies are almost always scaled, most have ctenoid (interdigitating) scales, their anal fins are short to moderately long, their upper jaws are usually not protractile, most have pharyngeal teeth, they almost always lack barbels...
The bulk of characiforms are small (don't tell this to a Pacu owner), many are colorful and popular aquarium fishes. They (and other fish groups) are ostariophysians (possess Weberian apparatus, a series of small bones connecting the gas bladder and middle ear... acting as an amplifier; goblet non-secretory cells... other features) with catfishes, cypriniiforms (minnows et al.)... Their diversity as a group is astounding... some reproduce outside the water, a few live on the scales of other fishes (lepidophagous), others are fin feeders...
Their taxonomy is a confusing mess. We will stick with Nelson here (3d ed. currently), but other folks raise and lower different taxa to different rankings, add other groups from elsewhere, subtract some that we have here to relocate elsewhere... Depending on who you believe, there are just one to sixteen separate Characiform families. For us here, we'll show, umm, ten families of about 237 genera and 1,343 species...
Chalceus show phylogenetic affinities with Brycon, and are hence sometimes included in the Bryconinae... Other systematists working with ostariophysian fishes would class them with the African Alestes (before Pangaea who knows how closely they were related?)...
There are four valid species comprising the genus Chalceus. Two come into the pet-fish markets on a punctuated basis, and are available more or less all year. The other two, Chalceus latus Jardine 184, and Chalceus taeniatus Jardine & Schomburgk 1841 are rare to the point of neither I nor many other veteran friends of the trade have seen them.
The Two Chalceus Species the Hobby Does See:
Like other "show" type tetras these fishes can and need be inspected carefully before purchase. The principal selection criteria, practices I've found helpful:
1) Time on hand. Don't buy new arrivals! Have seen whole shipments die "mysteriously" a few days after receiving. Wait a week or two before sending them on.
2) Bloody markings, cloudy eyes. Especially if there are ANY dead specimens from the shipment. Don't buy/sell these.
3) Behavior. Healthy, clean individuals are near the surface, aware of your presence (move slowly, deliberately in, out of the system). Bad ones act otherwise. See the example of one hanging out near the bottom. Not good.
Chalceus like the sorts of physical conditions as they experience in the wild. As large a space as possible (minimum three by one foot surface area per one specimen), with some planted, darkened space, open feeding area, semi-calm water. They don't like to "share" the surface of their tank space... unless the system is very large.
On first arrival/import, for biotopic presentations, breeding attempts, and general practice, ideal water conditions include slightly acidic to neutral pH, soft water and elevated temperatures (eighties F.). In actual practice, once Chalceus are "hardened" to captive conditions they are very accepting of a wide range of water quality.
Something to keep the water clean, circulated, aerated, but not creating a lot of surface disruption. Lots of surface approaching or floating plant material can discount above water discharges from hang on filters or above water outflows from canister types.
Years back in the wholesale livestock business (I worked for Charley Pratt in San Diego for a couple of years in their live-holding facility) we used "squirts" of organic acids (tannins, flavins) to initially reduce the pH and hardness (our tapwater is "liquid rock") for newly arrived livestock that came from softer, acidic waters. For a period of time we experimented with boiled (so it would sink) peat moss sandwiched between filter floss (we used, and cleaned... weekly, hundreds of modified pint ice-cream containers as filter bodies, PVC pipe in middle, notched at bottom, airstone/line in the middle...) to do same. You might consider the same low-technology.
Other than other similar, same species taking up their surface/hunting space, or very small tankmates, Chalceus are quite easygoing. I have kept them and seen others with them in general community tanks to quite feisty aggressive assemblages.
In the industry, these species are purposely kept very crowded (with covers over them!), which greatly reduces individual negative interaction. I have seen more than one kept in aquariums, and very nice displays of such in huge public aquarium settings, but for the "average" hobbyist (whoever, wherever...) would be better sticking with just one per tank... unless, trying to breed their Chalceus. For these attempts a screened or glass divider is a good tool to use to "introduce" the prospective parents.
For hobbyists, Chalceus are best placed in well-established systems that are not inhabited by fast moving fishes (better to place these subsequently if used), by the tried and true "floating bag" acclimation process, adding some system water every few minutes... If using a "drip-bucket" approach make sure and cover the container completely.
Reproduction, Sexual Differentiation:
Not known, recorded.
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
In the wild Chalceus cruise the surface, literally jumping at the chance to eat insects and their larvae near the waters surface. Additional principal stomach contents include crustaceans and worms of different sorts. In captivity these fishes need at least some meaty food items daily to do well. Ones fed on a steady diet of fresh foods show exemplary color, growth and activity. Though they will eagerly consume dried, prepared foods, don't forget to offer some fresh, frozen/defrosted, live meaty food daily (better in the early part of the day to prevent fouling).
Disease: Infectious, Parasitic, Nutritional, Genetic, Social
For freshwater fishes with large scales Chalceus are quite susceptible to ich and velvet. Happily they are not easily toxified by the usual medicines used for treating such complaints, and respond favorably to these as well as techniques involving elevated temperature.
When I think of the genus Chalceus members and their use in aquariums, a version of the "Got Milk" ad campaign comes to mind. I see a group of these stalwart characins on a billboard with the caption, "Got Cover" above them. Really, once acclimated, given space, some daily meaty food, and a complete top over them, these tetras are the epitome of simplicity to keep.
Gery, Jacques. 1977. Characoids of the World. T.F.H. Publications NJ. 672pp.
Nelson, Joseph S. 1994. Fishes of the World. 3d ed. John Wiley & Sons, NY. 600pp.
Sterba, Gunther. 1966. Freshwater Fishes of the World.
Pet Library Ltd. NY. 877pp.