Fish Food Cost Calculator
Enter the price and size of your fish food and how much you feed per day. The calculator returns how long the container will last and your cost per month and year — and warns you if the container will go stale before you can finish it, which is the real hidden cost of buying in bulk.
Calculate feeding cost
Works in any currency — the result uses whatever currency you typed the price in.
The formula — and the part everyone forgets
The arithmetic is simple: divide the container weight by your daily ration to get days per container, then divide the price by that.
cost per month = price ÷ days × 30.44
The part everyone forgets is freshness. Dry fish food is fortified with vitamins (especially vitamin C) that oxidise once the container is opened; manufacturers and feed studies generally put the useful life of an opened container at around six months, less in humid climates. A 500 g bucket at half the price per kilo is a false economy if your tank only gets through 100 g a year — you end up feeding nutritionally depleted flakes for months. That is why this calculator flags any container that would last much beyond six months.
How much does a fish actually eat?
Far less than most people feed. A useful reference point from aquaculture practice is that adult fish maintain condition on roughly 1–2% of their body weight per day in dry feed. A neon tetra weighs around a quarter of a gram, so six of them need well under 0.05 g per day — a single small pinch. The presets above are deliberately on the generous side of realistic community-tank feeding:
- Light (≈0.3 g/day): a lightly stocked nano or a handful of small tetras/rasboras.
- Moderate (≈0.7 g/day): a typical 60–120 L community of small fish.
- Heavy (≈1.5 g/day): a busy community or medium-bodied fish such as angels and rainbows.
- Very heavy (≈3 g/day): large cichlids, goldfish groups, or heavily stocked tanks.
If you want a precise number, weigh your container, feed normally for two weeks, weigh it again, and enter the difference divided by fourteen as a custom value.
Common mistakes
- Overfeeding. The most common beginner error in the hobby — and it costs you twice, once at the till and again in water quality, algae and filter maintenance. Fish are opportunists; begging is not hunger.
- Buying bulk that expires. As above — match container size to roughly six months of feeding.
- Comparing only price per kilo. Density differs: a gram of flake goes much further by volume than a gram of pellet, and wastage differs too.
- One food forever. Rotating two or three foods (flake/pellet, frozen, occasional vegetable) covers nutritional gaps. Budget for the rotation, not a single tub.
Frequently asked questions
How long does fish food stay good after opening?
Roughly six months is the widely used rule for flakes and pellets stored sealed, cool and dry; the printed best-before date assumes an unopened container. The food does not become dangerous after that — it just loses vitamins, which over time can affect colour and immune health. Keeping the tub away from the warm, humid tank lid helps.
Is one fasting day a week really fine?
For healthy adult fish in a mature tank, yes — many experienced keepers use one or two fasting days to mirror the feast-and-famine pattern of wild feeding and to reduce waste. Fry, very small species with fast metabolisms, and recovering fish are exceptions and should be fed daily. When in doubt about a specific animal’s health, ask a professional.
Why is my food cost so much lower than my electricity cost?
Because food is measured in grams while heaters are measured in kilowatt-hours. A typical community tank eats one or two euros/dollars of dry food a month, while heating and lighting the same tank usually costs several times that. Run the numbers in our electricity cost calculator and compare.
Is DIY or frozen food cheaper?
Frozen food (bloodworm, brine shrimp, daphnia) costs more per feeding than flake but is excellent as a rotation component. Home-made gel food can be economical for big, vegetable-eating fish like goldfish and large cichlids, but for a small community tank the savings rarely justify the freezer space — a tub of quality flake simply lasts too long to be worth undercutting.