Alternative name Atlantirivulus santensis.

Already back in 1906 W. Kohler described this species but Rivulus santensis was a poorly known killifish species from the Atlantic forest of southeastern Brazil that is redescribed by Dr. W.J.E.M. Costa in 2008.

The species is endemic to an area encompassing the middle and lower rio Ribeira de Iguape basin and smaller coastal river basins of São Paulo and Paraná states. Rivulus santensis is distinguished from all other species of the genus by the colour pattern of the caudal fin in males, in which there is a dark grey to black stripe on the dorsal margin of the fin, and another stripe that is similar but distinctively wider on the ventral margin. It is similar to R. haraldsiolii by having both the snout elongated and slightly pointed in a lateral view. Rivulus santensis differs from R. haraldsiolii in possessing 16 rows of scales around the caudal peduncle and one or two minute contact organs per scale on the middle portion of the flank in males, in contrast to 14 scale rows and two to seven prominent contact organs per scale.

Keeping and breeding is easy but a good cover of the aquarium is necessary because there ability to jump, even true the smallest opening, is unbelievable.

This species can, if there is enough space for them, housed in a tank with more males than one only and several females. If separated before and brought together again however, they can be very agressive to each other and fight to become dominant to others. The best way to have much offspring is to put a pair or an trio in a small tank from 10 liters with a small filter in it or with some airation. On the bottom some peat moss or dark gravel and a floating "mop" to give space for laying there eggs. The fish will, if they become a rich varity of life food, spawn during there whole adult life and produce daily between 5 to 15 eggs.

The eggs should be collected by hand and stored for about 14 days in a small container. Eggs are 1.6 mm and amber colored. It is wise, to add to the water you store the eggs in, some acryflavine to provent fungus coming up.

After hatching the young fry can eat fresh artemia nauplii without any problem. It takes 4 to 5 months to raise them to maturity. Often the number of males is far above the number of females. For some species this can become a major problem for the breeder as he has to raise many young fishes and so become able to distribute a few pairs to other hobbyists. Recent personal tests laerned that lower pH levels during the time of hatching gave a higher percentage of females. To achieve this I use some peat moss that I add to the container with the egss just before they are ready to hatch. This peat moss also is a good way to prevent eggs to become attact by fungusses.

There lifespan can be up to 3 years in captivity.

Remarks :

Max. size 6.5 cm.
Dorsal 9.0,
Anal 15.0,
D/A 11.0,
LL scale count (average)38.0
Pre- dorsal length to % SL – 77.0 %
Depth to % SL – 20.1 %