The specimens were collected from two shallow wells, at Fazenda do Seu Roque which is still occasionally used as a source of water for cattle, and the shallow, abandoned well at Fazenda do Lajeado. Both have similar physico-chemical characteristics, with the pH and conductivity typical of limestone drainages (Fazenda do Seu Roque: pH 6.98, conductivity 0.683 ?sm cm-1, 25?3?C and salinity 0?02; Fazenda do Lajeado: pH 7?0, conductivity 0?647 ?sm cm-1, 25?8? C and salinity 0?02%). Laboratory and field observations demonstrate that this species is predominantly a midwater swimmer; when undisturbed, it remains almost stationary in midwater, with the body inclined at a 10-40? angle, head facing either up or down, or moving slowly, with the mouth slightly open. It is apparently solitary and when in groups (in laboratory), they remain indifferent to each other, not schooling and if there is contact by chance, it is followed by mutual avoidance movements, usually (but not always) with the sma