Why is my goldfish eating gravel?

Written by james holloway Google
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Why is my goldfish eating gravel?
Goldfish sometimes eat the gravel at the bottom of their tanks. (Photodisc/Photodisc/Getty Images)

Brightly coloured, easy to keep and inexpensive, goldfish are one of the world's most popular pets. However, even these simple creatures can occasionally show some eccentric behaviour. One of the most common odd behaviours for goldfish is eating gravel from the bottom of an aquarium. Although this can occasionally be dangerous, there is no harm in it if proper precautions are taken.

Eating gravel

Despite appearances, goldfish that pick up gravel from the floor of their aquarium are not eating gravel. Natural bottom-feeders, goldfish are not eating the gravel but sifting through it looking for food. Excess feeding can mean they are often rewarded by flakes of food that have become lodged in the gravel at the bottom. However, this behaviour, although perfectly natural, can be hazardous to your pets' health.


Although goldfish normally feed in this way, sifting the substrate at the tank's bottom can be harmful. In some cases, the food they find among the gravel may be old and partly decayed; eating old food in this way can make the fish ill. Additionally, gravel can get caught in a goldfish's throat. Most of the time, they will simply spit the gravel out, but it is possible for a piece to get lodged, potentially harming the fish.

Choosing the right gravel

One way to prevent goldfish from sifting gravel at the base of the tank and possibly coming to harm is to use the right size of gravel. Pea-sized or larger gravel should be too large for these small fish to fit in their mouths. Alternatively, you may choose to keep the floor of the tank free of substrate. A bare-bottomed tank can be easier to keep clean, an important concern when dealing with goldfish.


If goldfish are searching for food among the substrate at the bottom of the tank, it may be because you're overfeeding them. Feeding your fish the exact amount they need and no more is a skill that comes with practice, but it's an important one for any fish-keeper. Follow the instructions on the food package carefully, adjusting the amount you feed your goldfish up or down as necessary to make sure there aren't extra flakes left over when they're done feeding.

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