temperatures rainbow darters

Dear All,
Ik like to have your advise concerning my rainbowdarters I obtained since 17 december last year; the day of the snowstorm in the Netherlands, the day I got stock in public traffic with my just bought precious rainbow darters in my backpack for 5 hours. Rainbowdarters are something very special for Europe/ Netherlands were I live and I do not want to take any risk with my darters, because I know, in summer months - july - temps in my fish shed rise to 26 Celsius. I keep them at the moment with temps from 2 - 6 Celsius and the seem to appreciate, and eating their bloodworms and tubifex now and then with eager.
Can I keep these fishes in water temps about 0 Celsius, or is 2 Celsius better as minimum temperature ?.

I am reading several things about temperatures; they should be comfortable in summer with temps in the mid 60 Fahrenheit, - 18.3 Celsius - but when I google a litte I am finding: at " The Inland fishes of the Missippi "; " Rainbowdarters show a wide range of temperature tolerance, with averidge winter and summer thermal maxima of 25.4 and 36.4 Celsius respectively. The high thermal tolerance and the large seasonal change, may allow rainbowdarters to occupy thermally variable streams during summer ( Kowalski et al 1978 ).
So my question is is it necessary to cool the fishes in my tanks in july?.
And I have intentions to breed with these fishes as well, I do have two breeding couples, are the young more sensitive for high temperatures then their parentz ?.

Regards, Casper

As long as your water is flowing and clear, rainbow darters can tolerate temperatures well into the upper 20s C. I don't think they would do well with temperatures above about 30 C, especially in stagnant water. Most fishes in the southern United States live near their upper thermal tolerance for much of the year.

Hi Fundulus,
Thanks for this information, now I know, watertemps in my tankshed never rise above 30 Celsius maximum 26 C.
Very curious if I can breed young, lots of information on this forum, with that I will succeed with breeding young darters.
Regards,
Casper

Very curious if I can breed young, lots of information on this forum, with that I will succeed with breeding young darters.

I think the key to breeding darters is separating fry and adults. My darters ate all of the fry in the tank, so the only way I would have seen fry is if I had removed the adults from the tank and put them in a separate tank. If you have a couple empty tanks that you can rotate your darters among, I bet you'd see fry in one tank after removing the adults to another.

Thanks Erica,
I will separate them after the mating, I think, I do separate males en females before as well, keep them together for 7 days, just enough to lay their eggs and then remove males and females, I do have space, and will put them in the tank with the rainbowshiners, aktually I did remove the rainbows as well from their spawning tank, last year, now I have 30 young rainbowshiners, which can breed this season as well.
Regards,
Casper

If this helps any... I have a spring fed creek on my farm (KY, USA) that has a thriving rainbow darter population. That creek never really gets above 60 degrees F, typically more like 50, probably due to the underground spring feeding it. Right now, it's hovering around 40 F.

My experience with rainbows is, they are one of the most durable darters, it's rare to lose one in a tank. (As opposed to some of the more delicate darters like speckled or emerald, which never seem to live more than a few months in my tank)