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Finescale Splitfin - Extinct in the Wild

Allodontichthys polylepis

Male Finescale Splitfin

At the 2016 ALA convention I purchased 5 fry of the Finescale Splitfin from the Rio de las Bolas in Mexico.  They were discovered in 1957, but a severe drought around 2000 destroyed the wild population.  Recently, Patrick Miller informed me that Mexico has lost all of its’ stock and there are probably less than 500 specimens in the entire world.  This fish is in the species maintenance program and very deserving of our efforts to save it.


Allodontichthys polylepis reaches a maximum size of about 3 inches.  They are strongly canabalistic of their fry, and the fry are very large when born (5/8 inch).  I only got 6 and 5 fry from the first 2 spawns, even though I took extra pains to save them.  They seem quite helpless when born and the parents are unrelenting in searching for them.  Unfortunately, I was raising those 11 fry in a fairly warm tank (78 degrees) and they got sick and died.  Males are slightly more colorful with a reflective blue and yellow in both body and fins along with a spotted and vertical body pattern, depending on the environment.  Males also have a white crescent edging of the caudal fin.  These fish are from cool, clearwater creeks and streams with sand or gravel bottoms, and it is recommended to keep them below 24 degrees Centigrade.  They may need a “winter resting period” and don’t reproduce much below 20 degrees Centigrade.  Clean water is essential, so extra water changes are needed.  They seem shy and slow to adjust to a new environment, yet can be quite aggressive once established, so wood, plants, and caves are helpful to give cover.  Their diet in nature is mostly insects, so brine shrimp, other meats, daphnia, and some spirulina flake seem to work well.


My lower aquariums stay around 70-73 degrees, so I placed the 5 fry in a 20 gallon alone.  2 potted plants, a cluster of anubias, and a ceramic cave were used for cover.  A pan-sponge filter was run vigorously and the bottom was free of gravel to make easier cleaning.  A pair of bristlenose plecos was included to “tidy up”.  They are slow growers and as they matured, one pair became dominate over the remaining trio, to the extent that the dominate female was the only one to have fry.  The female got fairly round when ready to deliver, but if I waited for her to get “square” in the vent area, she would deliver in the tank and some fry would be lost.  The most successful spawn was when the female was full sized (3 inches) and I picked the right time for her to deliver.  She was netted in a large 7X10 inch net that was left hanging in their tank with various plastic plants above and below for the fry to hide in with some daphnia to curb her appetite.  The birthing process lasted 12-14 hours and I recovered 12 fry.  I fed the fry newly hatched brine shrimp at first and later added flake food.  The fry grow slowly and seem hardier than the adults, but I emphasize the importance of cooler temperatures, as I believe that warmer temperatures were the reason the first 11 fry got sick and died.  They did not respond at all to salt and methylene blue medication.


For those livebearer enthusiasts who like a real breeding challenge, the Finescale Splitfin is a great choice, and helping to preserve a species that is extinct in the wild is an added bonus!

Female Finescale Splitfin