Why Did My Betta Fish Die?

When my first betta died, I was inconsolable, which is something that aquarists can never understand. It’s not always obvious what you did wrong, and you can find what’s behind your betta’s untimely demise. Often novice owners, such as I was, are ignorant of the essential elements that bettas need to survive, and their mistake is not neglect or lack of care.

Your betta fish died because you failed to ensure that your water parameters were safe, as well as your tank size, cleanliness, filtration, pH, and temperature. The other main factors that lead to betta’s death are unsuitable feed or feeding practices and stress factors within your betta’s tank.

It’s awful when you lose a fish, but the silver lining is that you can learn from your mistakes and ensure your next betta is happy and healthy. If you wonder how your Siamese fighter went belly up, here are some of the most common reasons your betta fish died.

Your Tank Conditions Were Poor

Several things can go wrong with your tank, resulting in the early demise of your betta fish. Betta fish are particularly hardy little creatures, and in their natural habitat or paddy fields and shallow water, they can withstand rather high levels of chemical and temperature fluctuations.

However hardy your pugnacious little bettas are, there are some fights that they cannot win when it comes to tank conditions. The most common causes of fish mortality in aquariums are as follows.

Blue and Magenta Betta

Improper Water Conditions 

Often fluctuating pH levels in your tank are to blame for a bettas death. Bettas thrive in water as close to pH 7, and although they may cope initially with fluctuations, they will succumb to illness or death over time.

Betas fare better in softer water. Often a simple mistake such as using the wrong water or unnoticed changes in temperature may explain your betta’s demise. The five most important factors to consider in a betta’s tank are the following.

Untreated tap water may contain harmful chemicals such as chlorine, chloramine, and heavy metals. You should always condition your water first with a fish-specific product or leave your tap water for 24 hours before using the water to fill your tank.

Distilled or purified water is not good either, as it depletes the trace minerals your betta needs to survive.

Tap water typically contains all the minerals your fish needs if you first remove the chlorine, chloramines, and other heavy metals.

Tank Cleanliness

Your betta produces waste that may elevate ammonia and nitrate levels, which can kill your fish, compounded by toxins from uneaten fish food. These problems are more severe in smaller, unfiltered tanks where ammonia levels may fluctuate rapidly.

If you keep your betta in an unfiltered bowl under 2,5 gallons (which is inadvisable and rather cruel), you should change 30-50% of your tank water every week. Even smaller tanks will need up to 100 percent water changes.

Tank size.

Although bettas have been unscrupulously touted as small tank fish, studies show that bettas in small tanks suffer severe stress and have higher mortality and shorter lives than larger ones. Your tank should be at least 5 gallons at a bare minimum, and 10 gallons is preferred.

Improper Filtration 

If your tank is under 2.5 gallons, a filter will do more harm than good. The string water movement caused by a filter in a small tank will cause the slow-moving betta considerable stress and lead to illness.

However, it would be best if you did not consider a tank below 5 gallons as a smaller tank for the health and well-being of your betta fish. Smaller tanks’ chemical levels can fluctuate and spike rapidly to toxic levels.

Tanks over 2.5 gallons large should have a filter system for several reasons:

  • Filters reduce waste. Filters filter your fish waste and food and filter out harmful bacteria.
  • Provide good bacteria. Microorganisms accumulate in your filter media that substantially benefit your betta’s health.
  • Oxygenation. Filters keep your oxygen levels stable and protect your fish from co2 toxicity.
  • Lower maintenance. Filters reduce the high maintenance of frequent high-volume water changes.

Incorrect Temperature 

Although the tough betta can withstand a bit of punishment when it comes to temperature, if they remain at a level too high or too low for extended periods, they will die. The ideal temperature for a betta is between 75-80℉.

Your betta is likely to die if your tank temperature is extended time over the mid 80’s Fahrenheit or below the lower 70’s Fahrenheit. Higher temperatures result in decreased oxygen absorption into the water. This will result in your fish literally drowning. Lower temperatures will result in your fish’s organs slowly becoming less effective as they struggle with something similar to what would happen with humans in lower temperatures

Even if your betta can survive at temperatures between ideal and these extremes, the betta will experience considerable stress, which leads to compromised immunity and susceptibility to disease.

Cold water also inhibits metabolic activity and leads to lethargy and diminished appetite. In tanks that are too warm, the betta will exhibit overactivity and tend to make burrowing motions in the substrate.

Stress and Betta Mortality

Stress may be the silent killer in humans, but did you know that your betta may also be at risk? Prolonged stress can cause a variety of illnesses in bettas and affects several vital functions, including:

  • The immune system
  • Endocrine function
  • Metabolism
  • Cardiovascular system
  • Respiratory system.

Stress factors are varied and include issues such as:

  • Tank overcrowding
  • Harassment from tank mates
  • Poor tank conditions
  • Rapid water changes

Food Related Betta Mortality

Correct feed and correct feeding practices are essential for a healthy betta. It would be best to choose a high-quality diet formulated explicitly for betta fish. You should also supplement your betta’s diet with a variety of protein-rich sources which can substitute their pellet feeding once or twice per week.

Great protein sources for bettas include:

  • Daphnia
  • Bloodworms
  • Brine shrimp

Bettas are opportunistic feeders in the wild, and so they fail to regulate their intake when presented with too much food. Overfeeding can cause bloat and lead to fouling of the tank water, which can kill your betta.

Overfed bettas can fall prey to digestive obstructions that may be deadly and excess weight gain, swim bladder problems, and obesity.


Besides natural causes such as aging, various factors can contribute to your beloved betta’s early death. However, if you take care to ensure that your tank perimeters are safe, your feeding is appropriate, and your bettas aren’t stressed, you should have years to enjoy your betta friend.