Natural temperature fluctuations.

[esoxlucius]

We see a lot of talk regarding the importance of keeping your nitrate in check by way of water changes. Not only nitrate, but also making sure you don't do anything which could cause an ammonia spike. We see a lot of talk about keeping your PH within a range, and not to let it wildly fluctuate. We see a lot of talk about, where possible, only stock soft water species in soft water and hard water species in hard water.

Basically we see a lot of talk about keeping your fish in the best conditions you can, which is fine.....but...... I've never ever seen a thread addressing daily swings in temperature from day to night, or seasonal swings in temperature. I bet all of us have our heaters set at x, y or z and leave them at that temp 365 days a year.

We address all the other stuff in an effort to replicate nature in a glass box but how many hobbyists actually have their heaters on timers to completely go off at night, or reduce temps at night? And how many reduce their temps drastically during the fishes winter season?

Fish in the wild, even tropical species, can go through some fair old fluctuations, sometimes within hours, nevermind seasons.

Would such temperature "alterations" in the aquarium environment promote breeding in some species, and could they benefit in other ways too from a day to day, season to season reduction/ increase in temps. Or would the constant up and down of the temperature cause stress and/or possible disease?

 

[aussieman57]

I believe it depends on the species and locale where they originate. For instance, I keep Gymnogeophagus balzanii in a heater less tank where the temperature may drop a degree at night and also fluctuates mildly (@ 5 degree drop) over the year. They could however benefit from a more robust seasonal cool down by placing them outside which I may do in the future. The closer to the equator a fish hails from would most likely have less temp fluctuations. For instance i used to live in Guam where the seasonal variation was hot, hot & real hot. The harbor temps pretty much stayed around 84 degrees. Now throw in the fact that most aquarium fish are tank bred and have never seen daily & seasonal fluctuations, and well, who knows whether they would benefit or not. Either way, I think most of us try to provide as ideal an environment as possible to provide a long life span.
Another difference between aquaria and natural water bodies is size and thermal strata. In a lake for instance fish will seek out areas where the water temp best suits them. Large water bodies have thermal strata where fish can locate a temp that does not differ much from day and night swings and/or seasonal changes (for tropical fish). For instance, when temps drop they can seek out deeper water where the temp is warmer and more consistent. Aquarium fish have no such luxury. So a large temp swing, let's say greater than 10 degrees over night can be stressful and possibly lead to problems.
Many species like Cory Cats can be induced to spawn by dropping the water temp. We've all done this.