Two new Rivulus species are described from a single locality in a stream near the village La Guadalupe, Alto Rio Negro, Guainía Dpt., South-eastern Colombia. Rivulus carolinae n. spec. differs from all congeners by combining a relatively small size, unique male color pattern and a characteristic caudal fin shape, and with a unique color pattern in females. Rivulus flammaecauda n. spec., differs by its robust size, by the presence of a unique striped and reticulated pigmentation pattern on the lateral portion of the body and a flame pattern on the caudal fin. The two new species were initially collected from a shallow, slow running, forest creek with black water. The type locality is only 2 km from that of another new species, described in this same volume of Killi Data Series. (Vermeulen & Mejia, 2020)

Rivulus flammaecauda and R. carolinae are known only from the type locality. The black water creek was located in primary forest under a thick canopy. Water depth was only a few cms, likely due to the flat terrain. The creek covered divided into several smaller streams and covered a wide stretch of the forest floor. The smaller Rivulus carolinae was taken in leaf litter in the shallowest parts of the stream; Rivulus flammaecauda was more abundant in deeper, open areas. Although the creek was on the Colombian side of the border, both species may also live in Brazil and Venezuela. 

Keeping and breeding is not easy and a tight fitting cover on the aquarium is necessary because their ability to jump, even through the smallest opening, is unbelievable.

This species can, if there is enough space for them, be housed in a tank with more than one male and several females. If separated before and brought together again however, they can be very aggressive towards each other and fight to become the dominant fish. The best way to produce numbers of fry is to put a pair or a trio in a small tank of about 10 litres with a small filter in it or with some aeration. On the bottom of the tank place some peat moss or dark gravel and a floating "mop" to give space for laying their eggs. The fish will, if they are fed a rich variety of live food, spawn during their whole adult life and produce daily between 5 to 15 eggs.

The eggs should be collected by hand and stored for about 14 to 30 days in a small container. Eggs are 1.6 mm and amber coloured. It is wise to add an anti fungus to the water you store the eggs in, to prevent fungal attacks.

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 males far out number females. For some species this can become a major problem for the breeder, as he has to raise many fry to enable distribution of a few pairs to other hobbyists. Recent personal tests found that lower pH levels during the time of hatching gave a higher percentage of females. To achieve this I used some peat moss that I added to the container with the eggs just before they were ready to hatch. This peat moss also is a good way to prevent eggs from being attacked by fungus.

Their lifespan can be up to 3 years in captivity.

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