Yes, Your Betta Needs A Heater
The question on whether a heater is needed to house a betta fish is one we get often, Many try to point out the fish “do fine in the pet store in a cup at room temperature” or that we do not employ heaters in our cups as an excuse as to why they should not need to provide their pet with a heater. The definition of “doing fine” is one that is where we see the biggest disconnect. Yes, a betta fish can live at temperatures under their ideal range of 75-82. The fact is these hardy fish can survive improper care. But alive and thriving are two different things.
When kept at an improper temperature fish will begin to be lethargic, their appetite will be suppressed, their digestion effected, and their immune system suppressed. They will be more susceptible to illness, more likely to have serious complications from any injury or illness, and less able to adapt to change. It takes time for these issues to slowly kill the fish, so a fish may survive in an air conditioned home or store environment for a while but make no mistake they are suffering. It would be no different then taking any other species (ie a husky living outside in 100 degree weather) into an environment that it is not designed for it may function but it is not thriving. If you would find it cruel to another species such as a dog or cat it is just as cruel to expect a fish to live that way to save yourself a $20 dollar cost which is what most budget heaters will set you back.
Our facility keeps betta in cups in heated rooms. Our stock rooms are kept at 80-84 degrees at all times for the fish’s comfort. Unless you are willing to keep your house temperature around 80 minimally you should provide your betta fish a heater.