bringing home gymnos soon, LFS temp issue?

[fish nanny]

Well my question is, should I keep my Yerbalitos at the same temp where they have been at for month or so ? Called the shop and they have them at 78+F .....OR should I slowly drop them to say 75........house temp here now is 69-73. I see they all all colored up and may already think it is summer, don't want to freeek um out, so I have heater I can set on low to say 75 or ?????????? any thoughts ??????? Love these guys, and don't want to screw up their inner clock..........thanks

[Bas Pels]

I'd cool the fishes from the 78 F to 73 F a bit slowly - say in 4 hours

Personally I would never heat a Gymnogeophagus tank - unless the temp would sink below 8 C (~48 F)

[notho2000]

In my experience with G. gymnogenys 'Arroyo Yerbalito', I have found them extremely tolerant of a wide range of temperatures. Last summer I put about 30 adults into my outdoor pond. In the heat of the summer they thrived (water temp 80+). As the water temperature gradually (and that's the key) dropped going into the fall, they showed no signs of a problem. I finally removed them from the pond on the 2nd of November, along with ~30 Lepomis megalotis (Kansas longear) and 16 goldfish. There was a thin skin of ice (1/4") on the pond when I drained it and caught the fish. All the Gymnos were fine.... showing incredible color and condition as were the other inhabitants. Throughout October , the pond temperatures were in the mid to low 40's and when I pulled the fish, it was 36oF water temp, air temperature 28 oF.. They suffered no ill effects from temperatures that were much lower than it gets in their native Uruguay. The 5" males were displaying prominent nuchal humps. It seems to me that the range of temperatures that this species can withstand is greater than in their natural environment. I'm not saying that these extremes should be provided, but a cool period is strongly advised. Maintaining them indoors at 68-75 oF is perfect. Here are a few pics of he Gymnos, one female seen in the net on that cold day, some longears "glowing in the fall sun, and then swimming in their over winter tank (180g) along with their pond mates. Hope this adds another perspective on temperature and wellbeing.
-Jim

[abarilot]

There are natural variations in temperature in the wild that happen all the time so a slight temperature drop is not going to screw up their internal clock.

I wouldn't worry about a heater unless your summers are not all that hot. I've had to use heaters in the past because the coast Southern California can be surprisingly cool in the beginning of summer.