Females have a single median ovary formed from the union of lateral organ rudiments, the fused internal walls of which form the median septum. Since 1972 when Fitzsimons wrote the above, one major systematic change affecting his words was Parenti's 1981 revision of the family Goodeidae to include two egg-laying genera within a new subgenus Empetrichthyinae . Currently I believe all taxonomists accept Parenti's conclusion that the egg-laying genera Empetrichthys and Crenichthys are indeed similar to what primitive goodeids must have been like and that by including them into the family its range is now extended north of Mexico's boundaries. My primary purpose in writing this account is to introduce to aquarists several species of the live-bearing goodeids and my impression as to their value as aquarium fishes. The first species I'd like to mention is my unquestioned favorite - the Rainbow Goodeid, Characodon lateralis .
Males are primarily red with yellow, green, black, and brown markings.
It is true of all goodeids and many fishes generally that body pigmentation may be enhanced by iridescence reflected from light sources back to the viewer - resulting in visual splendor not seen if the fish are viewed in poorly lighted situations. Rainbows can grow to 60 mm total length. The Rainbows are the most northern known viviparous goodeid and occur in springfed streams near Durango. In my Detroit water with pH of about 7.2 and 120 ppm of carbonate, a downward shift in pH can quickly become fatal to goodeids. I imagine hard, alkaline waters are much more to their well-being.