Common Name: Olomina
Latin Name: Brachyrhaphis roseni
Origin: Central America
Temperature: 70-76º F
Ease Of Keeping: Easy
Aggressivness: Mildly aggressive
Adult Size: Males to about 1.5″, females to about 2.5″.
Minimum Tank Size: Ten gallon
Feeding: Will readily accept commercial foods, but really appreciates live insects such as fruit flies.
Spawning Method: A hearty livebearer, not difficult to breed.
Comments: Brachyrhaphis roseni is another member of the rare (in the hobby at least) genera of fish, Brachyrhaphis. It is also referred to by the common name Olomina (along with many other livebearers, including the guppy in Latin America), as it is not a very commercially important fish.
It is from Central America, with the population that I am accustomed to coming from the rivers of Costa Rica. It is also one of the best looking species of the Brachyrhaphis genera. It is similar in looks to both rhabdophora and holdridgei, with black and red anal fin, as well as a dark netting pattern surrounding their scales. In addition though, it also has a light blue irridencence to it’s caudal fin that is fairly unique, and with a brighter red dorsal fin. They can also have dark verticle stripes on the back half of their bodies, which are most obvious on the males and fry. The females get larger than the males, getting to about 2.5 inches total length and fairly heavy, the males get to about a sleek 1.5-2″, and when in good color are the brighter of the pair, though the females still have quite a bit of color.
Brachyrhaphis roseni is also one of the easiest Brachyrhaphises to breed. The females drop about once a month, and typically seem to give birth to somewhere between 10-25 fry.
I have had good success with seperating the gravid females into a small tank (I use 2 gallon Critter Keepers) with a good amount of java moss or even plastic plants. The mother probably eats some of them, but there are still many survivors. I have never found any fry in their population tanks, so I am pretty sure that they like to eat their fry.
I keep, breed, and raise them at about 72-74º F, though I am sure that they wouldn’t mind it being a bit warmer.