What Happens If You Overfeed Your Fish?

Many children have fish as their first pet because it’s often thought they’re easy to take care of as they’re low-maintenance and don’t have too many needs. While this may be the case to an extent, there are still aspects of fish care that you must play close attention to, such as their food, as you don’t want to over or underfeed your pet fish.

Why Fish Are Often Overfed

Overfeeding fish can be a very easy thing to do because people forget just how small they are. Plus, with fish, one of the only ways to interact with them is through food. Not only does this mean people want to feed them more often, but the fish also begin to associate their appearance with the promise of food, which makes them appear hungry more often than they really are. Because of this, many fish owners don’t know how much or often to feed their fish, which can cause dangerous overfeeding. 

Here are some of the problems related to overfeeding fish:

  • Higher Ammonia And Nitrate levels

Both uneaten fish food and fish waste have protein in them that when broken down, turn into ammonia and nitrites that become extremely toxic to fish when there’s either too much of them, or they’re not cleaned out quickly and efficiently. 

  • Lower Oxygen Levels

Again, uneaten fish food as well as fish waste can decay in what’s called an aerobic process. An aerobic process is one that uses up oxygen and produces carbon dioxide in its place. When this happens, less oxygen is dissolved in the tank for fish to use. 

  • Altered pH levels

The breakdown of organic material, just as it lowers oxygen levels, can also alter the water’s pH level, which is an important factor to consider when keeping your fish tank’s water chemistry balanced. Different species of fish require different pH levels; thus, make sure to have an optimal pH range that you’ll want your water to fall into in order to keep your fish healthy. 

One effective tip for caring for pet fish is to be aware of your tank’s pH. Most fish species require a neutral pH, ranging between 6.5 and 9, however you’ll want to check each species’ requirements before introducing them to your tank. 

  • Fin Rot

Fin rot is really caused by stress, but overfeeding can be a major cause of stress in fish. 

  • Algae Bloom

Algae bloom is commonly seen in both ponds and tanks. It’s a kind of algae that multiplies when there are large quantities of organic material, nitrates, and phosphates in the water.

  • Mold

Too much food and, therefore, too much organic material, in the water can cause mold to grow on the gravel, plants, or other décor in either your tank or pond. This mold or fungus not only makes the tank dirtier, but can also be unhealthy to your fish.

How To Avoided Overfeeding

Now that you know the negative effects overfeeding can cause your fish, how to avoid overfeeding should now be addressed. There are many different techniques that can be used in order to control your fish feeding and ensure you aren’t falling into the category of overfeeding. These techniques include:

  • Using An Automatic Feeder

One simple way to do this is to invest in an automatic fish feeder, like the ones found on FishLab.com. An automatic fish feeder uses electronics to feed your fish daily, whether or not you’re there. This comes with a timer that allows you to program when your fish must be fed. All you have to do is remember to refill it when it gets empty.  

There are two main styles of fish feeders: rotating barrel and portion control. With barrel fish feeders, all you have to do is fill the barrel, and, then, it will rotate and drop a small amount of food into the tank as necessary. On the one hand, the portion control feeder is similar to a pill box—you fill pre-separated slots with the appropriate amounts of food, set the timer, and one portion will be released into the tank at the set time. 

  • Feeding On A Schedule

Automatic feeders will help prevent you from overfeeding your fish, but you’ll need to know what kind of schedule to set those feeders to. Most tanks will thrive if they’re fed twice a day. It’s better to have more frequent, but smaller feedings instead of larger portions of food less often. 

  • Feeding The Right Amount

Again, feeding the correct amount will be easier when using a feeder, but, first, you must determine how much you’re supposed to be feeding your fish. The best way to determine this is to watch your fish as they eat by feeding a small amount, paying attention to how quickly it’s eaten, and, then, add a little bit more at a time. 

As a general rule of thumb, anything your fish can eat within four to five minutes is how much they should be fed. Anything that exceeds that is, most likely, not going to be eaten and will contribute to an unhealthy tank. 

  • Removing Excess Food

While it’s best to avoid putting too much food in your tank in the first place, there are going to be times when there’ll be an excess of food in the tank for various reasons. When this happens, a good practice is to go in yourself and remove any food that hasn’t been eaten. Not only will this keep your fish from eating simply out of boredom, but it will also prevent the food from sticking to the bottom of the tank and causing mold, fungus, or other problems on your tank’s water health. 


As with any pet, overfeeding can lead to a slew of problems that could, eventually, lead to death. In fish, especially, being smaller and perceived as low-maintenance, it can be easy to fall into the trap of overfeeding. However, knowing the negative effects this can cause and, then, learning how to avoid those can be highly beneficial not only to the health of your tank and its inhabitants, but the overall happiness and wellbeing of your fish as well.

Emma Thompson

Hi, I'm Emma Thompson. Welcome to The Pet Town! I'm a Pet lovers like you and please feel free to get in touch with any questions. Enjoy your stay!

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