Unlike with a pet dog or cat, fish are quite a bit tougher for owners to communicate with effectively. This can be troubling for aquarium owners and hobbyists, since it can sometimes feel impossible to tell if your fish is happy or merely surviving.
But, there’s a silver lining! Using some simple physical and behavioral indicators, you can actually get a strong read on a fish’s overall mood and emotional health. Here are some key guidelines to focus on:
Look for Signs of Activity
Activity is one of the most surefire markers you can use to gauge your fish’s mood and wellness. When suffering from stress (often caused by common fish diseases), fear, or boredom, fish often become lethargic as they experience drastically reduced energy levels. They may start hiding in one area of the tank for long stretches, only emerging during feeding periods. Some unhappy fish will even stay hidden even during feeding, which I’ll touch on later!
But, you might also see the opposite extreme! Some fish panic under prolonged stress and start to swim in frantic, irregular patterns. This means that the most important metric isn’t exactly how active your pet fish is, but rather if its current activity level is out of the norm.
While a fish’s individual temperament and personality will partially determine its overall activity level, this is also highly dependent on species. Corydoras, for example, have a reputation for typically high energy levels, so it’s probably not cause for alarm if they’re moving around a lot. If, on the other hand, you notice frantic swimming by your betta fish, that might be a sign of swim bladder disease.
How Much Is Your Fish Eating?
Food intake is another quick and effective way of keeping track of your pet fish’s day-to-day mood. Though not a universal sign of unhappiness, members of most fish species eat less when undergoing boredom or stress. A huge variety of potential causes for this reduced mood and appetite might be the culprit, from bacterial infections to toxicity exposure.
If you notice that your pet fish has stopped eating (or is at least eating less), there are fortunately some immediate remedies you can try. The most pressing thing is to make sure the food itself is fine and hasn’t gone stale. Are the other fish in the tank also eating less? Switching out the food you’re adding to the tank might be the answer!
You can also try adjusting the aquarium’s water temperature or pH level, since these are frequent causes of abnormal feeding behaviors. If none of these solutions work, it might be necessary to contact a veterinarian or track down appropriate medication.
Unhealthy Fins and Scales
Symptoms of unhealthy skin, scales, and fins are also clear signs of an unhappy fish. Luckily, these symptoms are often fairly easy to spot. For example, your fish might show evidence of disease in the form of white spots, red and irritated skin, and protruding scales. Likewise, you might notice inflamed or rotting fin edges, which is another prevalent symptom of many fish diseases.
It’s important to note that, in this situation, cause and effect can go both ways. While suffering from a disease or infection can obviously lead to unhappiness in pet fish, the inverse is also true. Many stressed or emotionally uncomfortable fish will experience suppressed immune systems as a direct result of their unhappiness.
This weakened immune response can naturally lead to more frequent and severe illnesses. A mix of unhealthy tank conditions and underlying stress is, in most cases, the root of the more common illnesses in fish.
Observe Interactions with Other Fish
Stress can be both a cause and a result of aggressive, territorial interactions between fish. Some red flags to watch out for include hostile “patrolling” behavior (a prevalent type of betta fish behavior), fin damage from fights and nipping, and unusual hiding. Like I mentioned, this goes both ways. Fish who are getting attacked are naturally going to be stressed out and unhappy, but distressed fish are also more prone to lash out and attack their tankmates.
So, what causes these aggressive interactions and how can owners prevent them? In some cases, it’s a simple space issue. When too many fish are placed in too small of a tank, territorial behaviors start to emerge. This can be remedied simply by migrating your pet fish over to a larger aquarium.
On the other hand, these behaviors are often a result of a mismatch in fish species. Some species of fish eat tank mates, with bettas, archerfish, and red-bellied piranhas being particularly notorious examples.
Has the Fish Changed Size or Color?
While some signs of unhappiness in fish can be subtle and hard to spot, others have clear visual markers. Discoloration is a highly frequent symptom of chronic stress in otherwise colorful fish species, with duller body coloring, white spots, and red streaks along the fins all showing up regularly. Both darkening and paling of fin and body hue are possible, so be on the lookout for both!
Color changes in fish aren’t the only physical signs of stress and unhappiness. Size and shape can also suffer changes. Several species of fish, including rainbow trout and Eurasian perch, have been observed to grow to significantly smaller sizes when undergoing stressful conditions. Similarly, severely stressed pet fish may develop a weakened immune system and, as a result, display visible sores and protrusions. Often, these unhealthy growths will be readily apparent, even when viewed from a distance.
