It is difficult to know when exactly your betta will begin to exhibit signs of old age. This is mostly due to pet stores not knowing when their stock has been born. Bettas do not reach shelf spots until they are exhibiting colors which is around 6 months. Many pet stores sell bettas that are a year old or even older than that because they have already been used for breeding.
A typical betta fish that is well kept will live an average of 3 to 5 years. This can be shortened or extended based on diet, exercise and water conditions. As bettas age they will exhibit signs you could relate to many creatures. The changes are quite gradual so if you see your betta suddenly displaying the following symptoms over the course of a few days it is most likely due to disease rather than aging. Many of these symptoms will coexist with one another.
First you will notice your betta’s colors will fade over time. The vibrancy they possess starts to dwindle once they are past the prime age of breeding. If you notice your betta’s colors fade within a very short period of time it is more likely due to poor water conditions. Get your water tested right away by using an in-home testing kit or by bringing a sample of your water to your local pet store. Most pet stores will test your water for free.
You will also notice your beta fish starting to become more lazy. The lethargic state of mind will set in eventually and your betta will hang out on the bottom of his tank or lay around on a plant. If your betta becomes lethargic drastically again test the water and observe your betta for other symptoms that could point toward disease.
Eye sight is another thing that will deteriorate. In fact, many bettas acquire a thin white film over their eyes or “cataracts” in their later years. This makes feeding difficult for them. A betta fish with poor eye sight will try to lunge at food and miss it’s target. To aid in feeding I use my nail or a clean tool of some sort to hold the morsel very close to the mouth of a betta with poor sight.
Another way you can spot an older betta is based on how they hold themselves. A younger betta will have a back that curves the tail upwards. As bettas get older their back starts to sag and curve downward.
Compromised immune System
Chronic infections even with perfect water conditions are possible with older betta fish. Their immune systems are lowered due to older age and a lack of exercise.