Randy's Fishroom
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The Three Species of Rummy-Nose Tetras
part 2
- Randy Carey -

previously printed in the Jan/Feb '93 issue of the AquaNews,
a publication of the Minnesota Aquarium Society.
all rights reserved by the author and M.A.S.

Visual Differences
Although most aquarists fail to recognize a difference among the three Rummy-Noses, these species are usually quite distinguishable from their color patterns. The following sketches illustrate these major differences.
Petitella georgia

visual distinctions:

extent of red: The red recedes well past the gill only on H. bleheri. However, this coloration is not permanent.

spots at caudal peduncle: All three have a small black spot at the top of the caudal peduncle (the thinnest part before the tail), but only the two Hemigrammus species have one on the bottom.

black edging at base of anal fin: It is dark on P. georgiae, light on H. rhodostomus, and absent on H. bleheri.

mid line leading into the caudal: It is broad (and faint) on P. georgiae, narrower on H. rhodostomus, and virtually absent on H. bleheri.

bands on caudal: Broad on P. georgiae, narrower on the Hemigrammus species. Least amount of white on H. rhodostomus.

Hemigrammus rhodostomus
Hemigrammus bleheri

The best scheme to differentiate the three species involves three features: the lower caudal peduncal mark, the extent of red, and the mid-body line leading into the center caudal bands. By observing the presence or absence of these three features, the aquarist should be able to determine the species. (Logically, only the first two features are needed, but the extent of red is too important to aquarist to omit from this chart.)
lower caudal peduncle spot mid-body line red reaches well past gill
Petitella georgiae absent present no
Hemigrammus rhodostomus present present no
Hemigrammus bleheri
(most commonly available)
present absent when in favorable water conditions

All three species bear a black spot on the upper edge of the caudal peduncle (see illustration). If a similar mark is missing on the lower edge, the species is Petitella georgia. If the mark is present, check the coverage of the red.
If the red runs well past the eye and does not taper off until past the gill, then the species is Hemigrammus bleheri, the most commonly offered of the three. Unfortunately, if a H. bleheri is not in good condition, the red may recede toward the head, confusing it with H. rhodostomus. Thus, an additional feature is required for observation.
According to Gery, the black line on the posterior provides this distinction. Although not as dark as that on P. georgiae, the presence of this line signifies H. rhodostomus. In H. bleheri it is all but absent.
I would like to offer another observed distinction between the Hemigrammus species. H. rhodostomus exhibits thinner caudal bands--particularly the center one. If this center band has a width that could reasonably pass as a pencil's line, then the specimen is probably H. rhodostomus.

Differences in size, proportion, and position are easy to determine when viewing two of the different species, but difficult when looking at a tank of the same species. One should prefer keying on the features which differ by their absence or presence.
These species exhibit other visual differences.[9] An expert should be able to distinguish among the three by only the caudal markings. However, this requires memory of proportion and position. Furthermore H. bleheri differs from H. rhodostomus by having a more rounded "snout" and a slightly deeper body (not illustrated in the sketches).
Of course, many additional differences require closer examination, an option not readily available to the aquarist: Scale counts, dental configurations, jaw bones, et. al.
According to the Baensch Aquarium Atlas, the spawning of P. georgia has not been described and is assumed to be difficult. The Hemigrammus species have been bred, but the task is considered difficult. All sources prescribe very soft water, a pH around 6, and the inclusion of "bushy" or "fine pinnate" plants. H. rhodostomus is reportedly easier to keep and breed. Still, the Rummy-Nose has the reputation of being a difficult spawner.
The article referred to the scientific name as H. rhodostomus, an editor's note expressed the opinion that the photographed fish were the (then) newly described H. bleheri. Both of these species being very closely related, so one might assume that their spawning methods are quite similar. However, since the species are well segregated geographically, perhaps the water parameters are not the same. Given the location of bleheri (Rio Negro), I find it difficult to believe that bleheri would prefer the high 6's for spawning.
In a 1989 TFH article, Jiri Palicka offered a new element as he described his spawning success. He believed that aquarist were having difficulty because they assumed the Rummy-Nose spawned like most other Characidae. Rather than scatter their eggs, they "literally hang them up" on plants just below the surface. This is a similar behavior to that reported of some Nannostomus (Pencilfish). Furthermore, this species spawns after dusk.
Here is how that author repeatedly bred his Rummy-Nose Tetras: [10]
A 7 gallon tank is covered with black plastic on three sides and on the lower part of the fourth. A fern bunch is secured (securing is important) near the uncovered side. Demineralized water is treated with peat and carefully modified with sulfates and phosphoric acid. Calcium inhibited spawning and increased mortality among the fry.
Contrary to previous suggestions, Palicka lowered the pH to only 6.6-6.7 and the temperature was a quite low 68-72 degrees. At night time a 15 watt light scatters just enough light for the fish to see the plants but not enough to find the eggs after spawning.
The male begins his flirting about a half hour after dark and spawning continues all night long. The female deposits less than five adhesive eggs each time with a night's production of 450-500. Embryos develop in 18 hours at 75 degrees. The fry can eat newly hatched brine shrimp as first food.
My Specimens

The following discussion refers to my specimens in '93.

Five years later I still have 3 P. georgiae. They could be the same as I can't remember ever buying replacements.
I purchased eight Petitella georgiae and placed them in 10 gallon tank of about 80% reverse osmosis water and 20% water-softened water. I initially added black water extract, however this species is native clear water. The temperature is kept around 77 degrees, pH near 6.5. Within a couple of days four of the P. georgiae died, but I have lost none since. Judging from the size of the underbelly, I have two females and two males. With the current water conditions little or no red shows, but the fish are lively.
In the same tank are three specimens of what I assume to be H. rhodostomus. Their caudal markings perfectly match this species, but their posterior lines are too subdued to be classic examples. Perhaps they are the undefined H. bleheri aff. Two are females and the other a male.
None of these displayed much red when I first purchased them. I cannot explain it, but while one female still shows virtually no red, the other two display a solid red confined to the head. I recently used this pair in a spawning attempt. No eggs were found, but the watersprite was clearly disturbed.
All of these fish were timid at first. After a couple of weeks of acclamation, they now swim gregariously to the tank front to greet me when I come near. Perhaps it is in anticipation of my generous feedings of baby brine shrimp twice a day.
Of course I am keeping the common H. bleheri. They are kept in a 50 gallon community comprised of mostly characins. With water that is quite soft and slightly acid, these Rummy-Noses optimally display their colors of red, black, and white--textbook specimens. Perhaps these fish are younger than those of my other species, but I find them harder to distinguish between males and females.
[addendum '98:] I recently picked up a school of the common Rummy-Noses (H. bleheri) in a trade with a wholesaler. The red was so washed out that I thought they might be rhodostomus. The wholesaler said he was losing lots so he just gave them to me.
I put them in a tank with mostly r/o water and a pH around 6. I lost only one. Within a day they were swimming actively and sporting much more red. I suspect the problem most wholesalers and stores have with Rummy-Noses and many other "delicate" tetras is that they keep them in their tap water.

The pet industry has dubbed these fishes as "Crummy-Noses" since many die in transit. Were it not for their spectacular appearance and tight schooling formations, the stores would not bother to carry Rummy-Nose Tetras--or should I say Hemigrammus bleheri.
For some, a Rummy-Nose by any other name is still a Rummy-Nose. But as I said at first, not all Rummy-Noses are created equally.

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