About feeding a fish
The single most common way to harm aquarium fish is overfeeding — uneaten food rots and spikes ammonia, which is far more dangerous than a fish going hungry for a day. Fish should eat a tiny fraction of their body weight, and the aquarium as a whole, not the individual fish, is what you're really feeding.
How much should a fish eat?
Aquatic feeding is measured as a percentage of body weight per day rather than in calories. The table below uses about 1% of body weight daily — always adjust to the two-minute rule and your animal's condition.
| Body weight | Food per day (~1% of body weight) |
|---|---|
| 1 g | 0.01 g/day |
| 334 g | 3.3 g/day |
| 667 g | 6.7 g/day |
| 1.0005 kg | 10 g/day |
| 1.33367 kg | 13 g/day |
| 1.66683 kg | 17 g/day |
| 2 kg | 20 g/day |
What to feed
Match the food to the fish: flakes or micro-pellets for small community fish, sinking pellets for bottom feeders, algae wafers for plecos and otos, and frozen or live foods for carnivorous species. Variety improves nutrition and colour.
How often to feed
Feed only what the fish consume in about two minutes, once or twice a day. A weekly fasting day is healthy and helps prevent constipation and water-quality problems.
Common feeding mistakes
- Overfeeding — the number-one killer of aquarium fish via ammonia spikes.
- Feeding more than the fish clears in two minutes, leaving food to rot.
- One-food diets that cause deficiencies and dull colour.
- Ignoring the different needs of surface, mid-water and bottom feeders.
Weight & health
Overfeeding causes obesity, swim-bladder and constipation issues in the fish and, more urgently, toxic water. Underfeeding is rarely fatal short-term. When in doubt, feed less.
Frequently asked questions
How much should I feed my fish?
Only what they finish in about two minutes, once or twice a day — usually a pinch. As a rule of thumb, most community fish eat around 1-1.5% of body weight daily; large slow fish like goldfish need less.
How often should I feed aquarium fish?
Once or twice a day for most species, with one fasting day per week. Fry and very active small fish need more frequent small feedings.
Is it better to underfeed or overfeed fish?
Underfeed. Fish tolerate a missed meal easily, but overfeeding rots in the tank and produces toxic ammonia that can wipe out the whole aquarium.
Why is my fish always begging for food?
Many fish beg reflexively whenever someone approaches the tank — it rarely means true hunger. Stick to measured feedings and the two-minute rule regardless of the begging.