[GoldenToaster3300]

I have a male koi plakat betta, in a 7 gallon cube tank with a filter, but without a heater. However, I live in a tropical country with an average temperature of 30 degrees celsius during the daytime, reaching upwards of 34 degrees during particularly hot days. I heard the optimal temperatures for betta is between 25.5 to 26.5 degrees celsius. Do I need to cool my water? How do I maintain the water temperature if it fluctuates so much?

 

[Mbpoppy]

Hi!
You're correct that you don't want him to get too hot in there but on the other hand you don't want to cool him off too fast either.

If you don't have one, you'll need to obtain a food thermometer so that you know more accurately what his actual water temperature is.

I personally don't know of a better, more efficient method but on those days when you know it is going to be particularly hot and through the use of the thermometer you're seeing his tank temperature begin to rise, you could consider dipping out a gallon of his tank water, and add a gallon water that is two degrees cooler. In another hour, check him and see if you need to repeat the process.

 

[RussellTheShihTzu]

The only safe way to keep the temperature lower is with a cooler or a small fan. You can set up a small fan and have it blow gently over the surface.

 

[Antares78]

"How do I maintain the water temperature IF it fluctuates so much? " (The emphasis is mine)

Assuming the tank is always in a shaded area, the question you need to answer is what is the ACTUAL water temperature at various times during the day and night. The water will not react instantaneously to the ambient air temperature. I hope you mean the "average" HIGH ambient temperature during the day is 30 to 34 degrees Celsius. But, I know in some tropical areas, the night time temperature rarely goes much below 26 degrees Celsius.

You don't describe your particular situation. Housing in the tropics can be very different than what we are accustomed to in the states and other countries in the more temperate regions. Your tank may already be exposed to breezy conditions. If you don't need to see the tank during the very hottest part of the day, perhaps you could wrap it in some sort of insulation. (Bubble wrap?) Just a thought.

Remember, Betta fish are native to tropical areas of Asia. They live in bodies of water exposed to the sun and warm air. However, they are usually MUCH larger bodies of water than your tank. An issue you might have with your tank is a deficit of dissolved oxygen if the temperatures become elevated. Luckily, Bettas can take in a little air if they need to, but that is not ideal.

 

[Antares78]

I mention insulation, because we in the temperate regions can have the opposite problem. For me, an unexpected power outage in the dead of winter left me scrambling to find something to insulate my small 5.5 gallon tanks. Without electricity, our heating system doesn't work, and the temperature in the house can drop fairly rapidly. Depending on the reason, a power outage can last from mere minutes to days.