Signs of Overfeeding Goldfish

Overfeeding is bad for your goldfish's health.
i goldfish image by martin schmid from

Goldfish are greedy little critters and it's very easy for new owners to overfeed them. One meal a day is adequate but providing two smaller meals is more suited to their natural grazing behavior. Sludge, fish waste, algae and odor from poor water quality are signs that you should cut down on the fish flakes.

Uneaten Food

Goldfish quickly eat what they require as soon as you drop food into the tank. Anything left after five minutes is surplus to requirements so scoop it out with a net before it starts to break up and pollute the water. If you leave uneaten food, your goldfish will almost certainly be back for a second helping once it has digested the first.

Excess Fish Waste

Goldfish produce huge amounts of waste, so it’s worth remembering that what goes in, must come out. If you feed your fishy friend huge quantities of food you will inevitably see the evidence of their super fast digestive system. Long strings of waste still attached to the fish’s body are a sign that it has consumed far too much food.


Excess food creates an abundance of algae, an unsightly green or brown slime that can coat the surfaces of fish tanks and decor. Algae needs food to grow just like any other plant, so when you add large quantities of nutrient-rich fish food to your aquarium, you effectively feed the algae spores as well as your goldfish.

Sludge in the Gravel

If you don’t remove uneaten food straight away, it eventually sinks to the bottom of the tank and starts to decompose in the gravel. Goldfish may still try to eat the decaying food, which is far from ideal, and the rest slips between the pebbles to form a brown sludge that leeches a foul smell into the water.


Dirty water smells bad; a clean, healthy fish tank doesn’t have an unpleasant odor. The combination of rotten food, waste and bacteria provides a foul-smelling and potentially dangerous environment that can make your water toxic to goldfish if you do not address the water quality issue and cut down on feeding.

Unhealthy Fish

Poor water quality leads to unhealthy fish and overfeeding will eventually make your goldfish sick. Goldfish are covered in a special slime coat that protects them from bacteria and disease; unhealthy water conditions weaken the slime coat making the fish vulnerable to fungal outbreaks and bacterial infections that a healthy fish is able to fight off.

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