Q: LAB wrote,
I've been looking through your blog - so much helpful information. I'm currently cycling a tank (without fish), and am trying to regulate the temperature. During the day, I've got a light on for the live plants, and the water gets to about 80-82 degrees F, and at night, it gets cooler, so I've got a heater set to 80 degrees F. I was wondering how much of a temperature fluctuation the Bettas can handle safely? The time I'm most worried about is during the day, when the light is on.
I've got a 3 gallon aquarium, (the Eclipse system).
Thanks for your great blog and website!
A: It's true that rapid water temperature changes can lead to stress in aquarium fish and even thermal shock if extreme enough but the exact number of degrees that will cause damage can be difficult to pin point.
Water temperature fluctuations generally become a problem when they
1. Are drastic (alter by several degrees)
2. Are prolonged (fish that are kept at temperatures too warm or too cold on a regular basis)
3. Fluctuate over a short period of time
These temperature changes also effect the fish differently. A drastic temperature change can cause an immediate physical or behavioral change in the Betta. It may swim erratically, float on one side or appear distressed. Less severe fluctuations of just a few degrees over time may effect the fish in a less obvious way. For instance, the immune system can be weakened leaving the Betta prone to illnesses like bacterial infections or parasites. In these cases it may not be obvious to the fish keeper that the cause was stress induced by temperature changes.
The general health of the fish also comes into play. Weak or sick fish are more likely to feel the effects of temperature fluctuations. This is one reason why breeders won't ship fish that aren't in perfect health as shipping can often expose them to fluctuations of 10 Fahrenheit degrees or more.
That said, I personally try to keep my temperature fluctuations less than 2-3 degrees Fahrenheit in a 24 hour period (or 1-2 degrees Celsius.)In the summer this can be a bit more difficult so I try my best to keep my fish healthy by feeding them a balanced nutritious diet and keeping their water very clean.
One thing you can do is reduce the amount of time you keep the light on over your tank, particularly in the warmer months. As long as he's getting ambient light he'll be fine. The tank light is really more for your benefit than the Betta, unless you are using it to grow live plants that require a lot of light.
Aim for a temperature of 78-80F. A few degrees above or below that is fine, but of course best if you can keep it stable.