🐟 Fish · Free · No signup
What can live in your water?
Tank in the living room, goldfish bowl, or a dug pond in the yard — tell us the size and we'll tell you the real water volume, which fish fit, how many, and how to feed them.
20–30% weekly is the aquarium community standard for a healthy, stocked tank.
🌊 Your real water volume
–
liters
–
US gallons
Estimated real water volume — ~90% of tank size, minus gravel & decorations.
🐟 What can live here?
A comfortable community of
– small fish
(tiny fish like neon tetras or guppies, ~2.5 cm / 1 inch each)
📏 The classic rule of thumb: about 1 inch of slim fish per US gallon (≈ 4 L), and we keep 20% headroom for safety. It's a starting point — filtration, plants and maintenance matter just as much. Goldfish and koi break the rule completely (see below).
🍽️ How to feed them
Fish feeding can't be counted in grams like cats and dogs — but species have clear rules:
🐟 Tropical community fish (tetras, guppies, barbs)
A small pinch of flakes 1–2× a day, only what they finish in ~2 minutes. One fasting day per week is healthy.
🐟 Betta
2–4 pellets once or twice a day. Their stomach is the size of their eye — resist the sad face.
🐟 Goldfish
1–2× a day, what they finish in 2 minutes. Soak pellets first — dry pellets swell and cause swim-bladder trouble. They'll beg like dogs; don't cave.
🐟 Koi (ponds)
2–3× a day in warm weather. Below ~10 °C / 50 °F, stop feeding — koi can't digest cold food. Wheat-germ food for spring/autumn.
🧊 The honest rules (every species)
- Overfeeding kills more fish than underfeeding. Uneaten food rots and poisons the water.
- New tank? Wait 4–6 weeks for the nitrogen cycle before adding a full group of fish.
- Add fish gradually — a few per week, not the whole shopping list at once.
🔄 Weekly water change
Replace 25% every week
– liters
≈ – gallons · ≈ – bottles (500 ml)
⚠️ General guidance only. Stocking level, filter capacity and fish species change what's right for your aquarium — when in doubt, test your water and ask an aquarium specialist.