When Stress Overcomes your Betta


Cat Fish, originally uploaded by phlora.

Q: LL wrote,

I am struggling with the death of my betta. I lost him on Friday, after having him for a year and 4 months.

He was doing just great until 2 months ago when he started hanging around at the bottom of the tank more. I did tons of research and thought the problem was two-fold: water was too cold and I was not leaving some of the water in the tank when I cleaned it. So, I ran to the store and bought a good heater (I have a 5 gal. tank with air filtration and a light) and for the last two cleanings, I vacuumed the gravel and emptied some of the water, but not all of it.

This was the first time EVER that I didn’t do a 100% water change. Now, I am afraid that by not cleaning the tank properly (I still don’t know how to clean it since you aren’t supposed to change it 100% and yet when I stopped doing that, coincidentally, he died), the PH level plummeted (I had it tested and it was very, very low) and that is why he died.

I put him in an iso tank for the last few days he lived, but it wasn’t enough to save him. Since a lot of folks say they live for 2 or more years on average, I wondered if age was a factor or not. I am agonizing over this and afraid to get another betta if I did something to kill my beautiful Nemoby.

Did the gradual lowering of PH kill him? If you are supposed to leave some of the water at the bottom when you clean, how much? How much of the residue should be vacuumed out? How do you know if you have enough of it out so the PH doesn’t drop?

I appreciate any suggestions toward what killed him and and help in getting through this sad experience.

A:I’m sorry to hear about the loss of Nemoby. I have lost many over the years, some natural causes and some to errors I have made and like you I have been saddened by each loss.

Sometimes the death of a Betta occurs quickly and without warning and it can be difficult to determine the cause. From your description of the events there are a few possibilities. I will start with the pH crash. A pH crash occurs quickly and may be the result of very low carbonate hardness (kh), which is also called buffering capacity. Buffering capacity regulates the pH in the water and when it is very low you are more likely to experience rapid changes in pH. When I lived in Boston, the water’s buffering capacity was very low and I experienced pH crashes from time to time that caused sudden death to several fish at a time. These crashes usually cause death in a matter of minutes to hours if severe enough. In your case Nemoby was showing signs of stress 2 months before the pH drop so something was probably stressing him early on. The pH situation may have caused added stress but not necessarily death unless it happened very quickly. You didn’t mention the exact pH levels or the rate they dropped so it’s hard to say how serious a problem the pH was. Bettas can live in a variety of pH levels but stability is the key. So even if it was 6.0, he probably would be fine.

The type of water change you do (partial or full) depends on your aquarium set up. If your tank is established and has completely gone through the nitrogen cycle then you want to perform partial water changes of around 20% to keep nitrates at bay. If you prefer not to cycle your tank then 100% water changes are best to avoid the build up of ammonia and nitrite. In order to know if your cleaning regimen caused stress to your Betta I would have to know what the ammonia and nitrite levels were when he died. It seems unlikely, however, that they would get way out of hand after only one partial water change.

I can only guess that a variety of stressors lead to a weakened immune system over time and he eventually passed away. The life span of Betta vary and most live around 3 years but breeding, care and good genes all play a part. Store bought bettas are usually around 6 months to a year old at purchase and often don’t live as long because of stress they endure before purchase. (I.e. cold water, ammonia poisoning, poor nutrition, etc)

One thing I can say with certainty is your little Nemoby was much better off living in your care in a warm, clean home where he was well fed and loved then on any store shelf. The fact that you cared for him for well over a year is a testament to your abilities. All bettas die eventually and while it is sad we can take solace knowing that we provided as best we could and that our pets were loved and cared for.

I hope that when you’re ready you will give another Betta a good home and a chance at live away from the pet store.

Here are some links to articles that will help you with some of your specific needs. This first one talks about the nitrogen cycle and whether to do partial or full water changes. – Preparing a New Home for your Betta
The second link goes into detail about water changes and frequency. – Water Changes: Frequency

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Christie F is a Betta splendens hobbyist that enjoys spending time caring for her fish and helping new betta keepers learn the ropes. More posts by:

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