...from that article... I'd try to replicate this:
The Environment
The environment where Herichthys minckleyi is found is very specific. It is formed by warm crystalline water springs with visibility generally greater than twenty meters (66 feet) and with very stable temperatures. Measurements made over a ten-year period in Laguna del Mojarral, showed a range from 33.5° to 34.0° C (92.3 to 93.2°F), a variation of just 0.5°C (0.9°F)(Arnold, 1972), with maximum variations at surface level of 5°C (9°F)....
The thermal springs have bottoms with dense detritus layers over a rocky substrate with areas of exposed rocks. Other springs have gypsum floors. Some calcareous rocks can also be observed along the shores. Plants of the genus Nymphaea (water lilies), with floating leaves and beautiful flowers, are the most abundant aquatic vegetation. Canes and weeds occur along the edges of some lagoons along with overhanging desert vegetation. Other aquatic plants without leaves can also be observed in some springs (e.g. Poza Churince).
The pH is on the alkaline side. Measurements taken by me during several visits have ranged from 7.6 to 7.8, with general hardness readings of around 55 German degrees.