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The Dangers of Uneaten Fish Food

Aqueon Blog Dangers of Uneaten Fish Food

Let's face it, it's fun to feed our fish! It's one of the few ways we get to interact with them, and it's a great way to get shy fish to come out so we can observe them. Unfortunately, overfeeding is not only detrimental to your fish, but also to the overall health and well-being of your aquarium. Here are some negative effects uneaten food can have on your aquarium:

  • Uneaten fish food releases toxic ammonia and nitrite as it decomposes. This is especially dangerous to newer aquariums where the nitrifying bacteria that gets rid of these toxins hasn't had a chance to fully develop. High ammonia and/or nitrite levels can stress and even kill your fish. This problem is even more severe in small aquariums where toxins can reach lethal levels quickly.
  • The decomposition process uses oxygen, which lowers the dissolved oxygen content (DO) in the water and stresses your fish. Since DO naturally decreases at higher temperatures, the effects are more severe in warmer aquariums that are in the upper 70's to mid-80's. Poor water circulation compounds the problem.
  • The breakdown of organic material lowers pH by releasing carbon dioxide, which is converted to carbonic acid in water. In soft water aquariums or those with low buffering capacity, pH can quickly drop below the safe range for many fish species, especially those that prefer more alkaline or basic conditions.
  • Uneaten food can clog your filter, decreasing its efficiency and reducing circulation in the aquarium. This may result in a low dissolved oxygen content, a drop in pH, a rise in ammonia and nitrite levels, and general stress to your fish. Decomposing fish food also offers a place for mold and fungus to grow.
  • Excess food causes a rise in nitrate and phosphate levels, which contributes to increased algae growth. Poor water quality also stunts your fishes' growth, causing their colors to fade and lowers their resistance to disease.
  • Fish can suffer from obesity and the negative effects on their liver, kidneys and other internal organs.

Follow these tips to avoid overfeeding and prevent uneaten food from accumulating in your aquarium:

  • Feed your fish only what they can consume in 2 minutes or less, once or twice daily. Any more than that will probably never be eaten. Overfeeding is not a matter of how many times you feed each day, but rather the amount of food per feeding.
  • If your fish still seem hungry after 2 minutes, give them a little more but food should not be raining down on the bottom of the aquarium. Remove any food that remains after 5 minutes with a siphon or fine mesh fish net.
  • Fast your fish for one or two days a week.
  • Feed according to the number and size of fish in your aquarium, not according to how large the tank is.
  • Restrict feeding responsibilities to one person in your home or workplace. Assign a fill-in when the primary person is away, but make sure they are properly trained in the appropriate amount to give per feeding.
  • Have plenty of scavengers such as catfish, loaches, snails or shrimp in your aquarium to help clean up the bottom.
  • When switching to a new food, feed sparingly at first, as fish may not take to it right away.
  • Feed the right types of food, in the right format. For example, fish that are used to feeding at the surface will generally not look for food on the bottom, and while bottom feeders are known to come to the surface for food, it is better to feed them sinking foods. Avoid feeding large fish small particles of food or the fine dust that settles on the bottom of the container. Remember to break up large flake or pellet foods for smaller fish. Feed carnivorous fish protein-based food, and herbivores plant-based food to avoid excess waste from undigested food.
  • Feed only fresh, quality food, as your fish may refuse stale or low-grade foods.
  • Choose a filter that is slightly oversized for your aquarium and clean it regularly.
  • Perform a 10% water change weekly or 25% bi-weekly and lightly vacuum the bottom in the process.

When you're away from home, use these techniques to avoid problems associated with uneaten food accumulating in your aquarium:

  • If you'll only be gone for 2 to 3 days don't worry about your fish, they'll be fine if they're not fed.
  • If you'll be away longer, consider using an automatic feeder. Test it out for a few days before you leave to make sure it's dispensing the correct amount of food. Have a friend or neighbor check on it every few days during long absences.
  • Do not feed your fish heavily the day before you leave – this is the worst time to have uneaten food in your aquarium, as there will be no one there to take care of any potential problems.
  • If you hire a "fish sitter", make sure it's someone with fish keeping experience, and make up pre-measured packets of food for them to dispense every 2 to 3 days.

Overfeeding is one of the most common problems aquarists deal with, especially when new to fish keeping. Remember, your fish will not starve if they miss an occasional meal. You can cause far more harm by feeding too much than by feeding less.

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