Paraguay is not so easy, if you want to describe the water values there.

East sides of the Rio Paraguay it is very dry and hot.

Just in the very north, where the south ending of the Pantanal is, there is much water.

In the east in summer, some water holes can have a temperature from more than 35°C and the water can have much salt.

At the west side of the Rio Paraguay there are many forests and the temperature is not that high,as in the east. 

In winter everywhere in Paraguay it can have less then 10°C, but the water temperature does not go under 15°C.

All in all I would say, that 20-26°C is a good temperature to care fishes from Paraguay.

The pH level should be a little acid or neutral. The kh and gh should not be higher than 15°.

In Paraguay there live many several species, like several Crenicichlas, Astronotus crasipinnis (just from the north to the middle), Mesonauta festivus (just in the north) Satanoperca pappaterra (just in the north), several Corydoras and Tetras and many other big Plecos, Catfishes.

The underwater Biotops can look very different. Here are some of my videos, where you can see how it can look like, but there are much more different Biotops.