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Darter Goodeid, "Goodeid or Baddeid?"

Allodontichthys tamazulae

Male Darter Goodeid   Photo by Darrell Ullisch


The Darter Goodeid, or Peppered Splitfin, is a new livebearing fish from the Rio Tamazula, Mexico.  Although males can be somewhat quarrelsome, the “bad” reputation stems from their ability to kill their fry.  This is not a routine fry-eating parents’ case.  These fish seek out their newborn fry with a vengeance!  And it isn’t as if they can swallow the fry whole, since they are about 10 mm (3/4 inch) long, and A. tamazulae does not have a large mouth.  It doesn’t help that the fry seem somewhat sluggish and heavier than water when they are born, either.  One is lucky to save a couple live fry from each batch, most being found dead.  However, this trait adds to the mystery and challenge of breeding this fish, which I like.


It is not an especially colorful fish, having a grey color to the body with a few dark pepper spots.  Males seem to have darker and more spotting at the base of the dorsal fin, although this can be variable.  They come from higher elevation streams, which indicates a need for fresh, cool water.  They have a hearty appetite and eat a variety of foods, including live, flake, and frozen.  I think some vegetable matter can be beneficial for them also.  I placed a few seashells in their tank to keep the water on the hard side.  Ideal temperature is 64-72 degrees, although I kept mine at 74 degrees and they did well.  My female reached 3 inches, but I suspect they can get slightly larger.  These fish should have lots of room and clean water to do their best.


The pair I obtained in January of ’07 was placed in a 20 gallon long tank with some rocks and caves for hiding and some weighted anubias nana plants for cover on the glass bottom.  Floating hornwort was present also, but did not provide any cover for the fry, as I later found out that they remain on the bottom.  When the female became ready to deliver, more cover was placed in the tank.  She was about 2 inches long and quite large in girth, so I expected a number of fry to survive.  The next day when I checked the tank, she had given birth.  As I was removing the plants and rocks, I noticed one fry—and the female started chasing it while I was trying to net it!  After all the cover was removed, I only found 2 dead and 2 live fry, much less than I expected.  It seemed that the glass bottom with no gravel made it easier for the parents to find and kill the fry.  They probably end up eating some by picking them apart.


The next attempt I moved the female to a smaller tank jammed with plastic plants where she could hardly move around.  Pregnant females must be moved in water (e.g. a cup) and not picked up in a net or they will be damaged.  I put live food in the tank and waited for a week, but no fry, so I placed her back in the 20 gallon with cover.  Of course, she had them soon and I only saved 4 live fry.  I noticed her swimming up and down the glass sides of the tank just before.  Likely vigorous swimming action is needed to help the birthing process, which was not available in the smaller tank.


For the next batch I had to try something different!  I netted the pregnant female in a large 10 inch by 7 inch net and hung it in the tank with about 2 inches of dense plastic plants in the bottom of the net so the female could not get beneath them.  There was adequate swimming room above the plastic plants for her, and I placed a glass cover over the net so she could not jump out.  Some daphnia in the net probably helped.  The next day after removing the female, I collected 15 live and 1 dead fry from the plastic plants, a much better ratio!


Some have asked about how to tell when a goodeid female will have her fry.  One way is to note when the posterior portion of her body appears “square”.  This can vary with species, but is quite discernable in A. tamazula.  Yet in fish with longer gestation times, this can last for a week or more.  I have found that close observation of the females vent area will indicate a slight protrusion about 24 to 36 hours before giving birth.  The fry are shy and take about 4-5 days before they are swimming well on their own.  Newly hatched brine shrimp is a good starter food.


In conclusion, Allodontichthys tamazulae is an interesting, active, and fairly easy to keep fish.  The challenge is in breeding this fish and saving the fry.  I hope my observations will help others to enjoy and succeed with this fish also.