KuhliLoachTrainerKuhliLoachTrainer:
Thanks for linking that 2020 surubi study, I really enjoy reading it in general so a nice surprise to seePersonally, I take recommended temperature ranges from online sources with more than a grain of salt because a lot of the time they can be shockingly far off. I'll give you some examples:
-Turquoise/umbee cichlid. These are often imported from the Magdalena: refer back to what I wrote about how chilled the waters of the Magdalena are. I have seen numerous sick umbee cichlid threads on Monster Fish Keepers where the fish were being kept at temperatures in the high 20sC (which a bunch of online sources recommend), for which Duanes recommended lowering the temperature on the basis of the colder Magdalena waters.
-Central American cichlids in general. You can find a thread about this by Stanzzz7 on Monster Fish Keepers titled ‘Are we keeping our cichlids too warm!’
-Some Rift Lake African cichlids. I don’t remember many specifics here but I do remember Millingu reporting theirs doing well at temperatures around 22C, around 2-6C colder than several online sources recommend. If you ask them I am sure they’d be happy to elaborate.
-Black, striped, and neon kuhli loaches plus Burmese loaches. All of these species are recommended to be kept in the mid 20sC to 30C by various online sources, but I have kept mine at 19C for months if not years with no issue whatsoever.
-Cardinal tetras. I can’t find this study no matter how hard I look, but I’ve seen one that showed cardinal tetras have notable (as in >3%) mortality over time at >28C compared to 25-27C having no mortalities, but a lot of online sources recommend >28C temperatures for them.
-And then there’s also a perhaps unexpected source, River Monsters. If you watch the episode River of Blood, Jeremy’s fishing in the winter where the air temperature is considerably colder than 22C, the water temperature is stated to be cold enough that most dorado aren’t feeding, he's wearing a jacket, and despite all this he catches a big surubi that did not stop feeding. That would rather contradict the lower ends of the recommendations you listed.
Hope this helps
Fish Story:
Thank you so greatly! For the last point, as being relatable to our corruscans case, yes, you are probably correct but our concern is the high end of the range and a potential need for a cool off or not. Was the River of Blood the San Francisco river?
You’re very welcome
As for our case, I think it’s less about the temperatures of the high end of the range (Argentinian summers can be hot on average and have considerable heat waves into the mid high 30s and even 40sC, there is almost certainly overlap with Naples’ summer water temperatures at some points) and more about the duration of the high end of the range. One thing I forgot to mention about something that might necessitate a cool off is the fact that the warmer water is, the less oxygen it will hold. For example, water at 12-15C (the temperature I suspect Jeremy Wade’s surubi was caught in, going off of some online sources for the winter water temperatures of the southern parts of the Parana River that was in River of Blood) can hold 20+% more dissolved oxygen than water at 24C+, which your water is for much of the year (in a February 8 2022 comment on Monster Fish Keepers, you say your water is 22-26C in the cooler time of the year and 29-32C in the warmer time of the year).
If Widmer is kept too warm for too long without cooling off, that uninterrupted stay in the low end of his dissolved oxygen range could prove detrimental even if it doesn’t outright kill him (ie: the stress could weaken his immune system enough for parasites to take over). For reference low oxygen has been known to cause health problems in other fish, Duanes has said rheophilic species can get fungal and bacterial infections when they don’t have enough dissolved oxygen.
Also I’ve seen Wednesday13’s comment in your journal, I appreciate his input as always
Not having any experience with any species of surubi I can’t say for certain, but I suspect that the surubi in the Brazilian tanks he is talking about are sourced from or farmed in the warmer parts of their range given how well they are doing at the tropical temperatures: refer back to what I wrote about the Brazilian cities near the northernmost parts of the Parana, Paraguay, and Sao Francisco rivers having the same tropical climate as Naples. Not to mention that another reason they are likely to be from those warmer Brazilian parts is because they are in Brazilian tanks, so because P. corruscans is native to Brazil, I think it's very likely those individuals are locally sourced as opposed to potentially being exported from a colder location in Argentina, which would seem unnecessary to do if P. corruscans is native.The example he gave with wels catfish is also interesting but I don’t know how applicable it necessarily is to an extrapolate here because the impression I get is that wels catfish seem to do unusually well in warm climates by colder-water fish standards. If memory serves, Jeremy Wade mentioned both in his book and in the European Maneater episode of River Monsters that the wels catfish in the Rio Ebro in Spain do better than the wels in the more northern, colder climates they are actually native to because of the warmer climate. Whereas for P. corruscans, I have a hunch that the standard issues from too warm water apply, given how that’s the case in Duanes’ experience for the cichlids from the same sorts of areas.
Fish-Story
Thank you. Too bad YT is very ill suited for such long, in depth discussions. I have to manually scroll through 30-40 pages to find the comments. It's too time consuming.
