Fish from orinoco river like it cold???

[TheTerminutter]

I searched up the temperature of the orinoco river, and according to Brittanica the orinoco can get up to 95 at the hottest, but the average temperature is 64-69 most of the time. But most websites tell me to keep fish from the orinoco at around the mid 70s.
Which temperatures do myleus and pacu actually prefer?

 

[tlindsey]

64-69

That's too cold for either. I have 2 spotted silvers in aquarium water temperature 74°.
Im not going to go lower than that.

 

[duanes]

Pacu, and Metynnis are some of the most widespread fish in S America, and a number of species and variants are found in the south, in Argentina and Uruguay where water gets quite cold, rivers and lakes even gets iced during winter, so its no surprise some are also found in the coolest waters in the north.
I would imagine knowing your location variant, would be important before experimenting.

The shot above is a river in winter, not far from Buenos Aires, Argentina.

 

[FJB]

I believe the information from Britannica you are citing comes from the paragraph below.

That paragraph refers to air temperature, not water temperature.
It is unclear what is meant by "Orinoco River", as it covers a vast area beginning on southern Venezuela, flowing west toward the border with Colombia, following north along it, and then changing east through Central and eastern Venezuela.
Parts of the Orinoco and its tributaries in Colombia and Venezuela start on highland (with lower temperatures), but then flow eastwards through low lands (the Llanos) that may be considerably warmer. There is bound to be a great deal of variation along that vast area, which receives a number of tributaries.
Unfortunately it seems hard to get good water temperature numbers for the portions of the Orinoco watershed as it travels through lowest land (central and eastern Venezuela). Altogether, I suspect average water temperatures in the eastern portion of the Orinoco are higher than the paragraph above would lead to believe (say past the place where the main Orinoco River changes from flowing on a mainly north direction to a mainly eastern direction, at around the Rio Cuchivero). Past that (which is about halfway on the Orinoco basin), the land elevation (altitude) everywhere is less than 100 meters; there is no way temperatures are very low at that elevation and that close to the Equator.

Regarding temperatures relevant to Myleus and pacu and others - I guess distribution data (and water temperature data) are quite incomplete. However, Mylosoma aureum and Serrasalmus spilopleura (the only ones I see with distributions described specifically as "Orinoco", but not certain where on the basin). For those, suggested temperatures range up to 23-28C (73.4 - 82.4F) (See Baensch and others). A number of other Serrasalmids do occur on the Guyana Shield, a large area north and east of the Orinoco, which is somewhat different and not sure if relevant to your question. And yet, suggested temp ranges for those fish are the same (23-28C).
From the above, I would say that aquarium temperatures around 76-78 (or 80 F) would be best for those fish, being middle of the range.

 

[TheTerminutter]

I believe the information from Britannica you are citing comes from the paragraph below.
View attachment 1513949
That paragraph refers to air temperature, not water temperature.
It is unclear what is meant by "Orinoco River", as it covers a vast area beginning on southern Venezuela, flowing west toward the border with Colombia, following north along it, and then changing east through Central and eastern Venezuela.
Parts of the Orinoco and its tributaries in Colombia and Venezuela start on highland (with lower temperatures), but then flow eastwards through low lands (the Llanos) that may be considerably warmer. There is bound to be a great deal of variation along that vast area, which receives a number of tributaries.
Unfortunately it seems hard to get good water temperature numbers for the portions of the Orinoco watershed as it travels through lowest land (central and eastern Venezuela). Altogether, I suspect average water temperatures in the eastern portion of the Orinoco are higher than the paragraph above would lead to believe (say past the place where the main Orinoco River changes from flowing on a mainly north direction to a mainly eastern direction, at around the Rio Cuchivero). Past that (which is about halfway on the Orinoco basin), the land elevation (altitude) everywhere is less than 100 meters; there is no way temperatures are very low at that elevation and that close to the Equator.

Regarding temperatures relevant to Myleus and pacu and others - I guess distribution data (and water temperature data) are quite incomplete. However, Mylosoma aureum and Serrasalmus spilopleura (the only ones I see with distributions described specifically as "Orinoco", but not certain where on the basin). For those, suggested temperatures range up to 23-28C (73.4 - 82.4F) (See Baensch and others). A number of other Serrasalmids do occur on the Guyana Shield, a large area north and east of the Orinoco, which is somewhat different and not sure if relevant to your question. And yet, suggested temp ranges for those fish are the same (23-28C).
From the above, I would say that aquarium temperatures around 76-78 (or 80 F) would be best for those fish, being middle of the range.

Ohhhhh air temperature. Someone should reword that Britannica article