Livestock & Feeding Calculators

Fish first, numbers second

Every decision about livestock starts with the animals: how big they grow, how they behave, what they need from water and company and how much waste they make. The tools on this page turn those needs into planning numbers, but the numbers are only as good as your research into the species you want. A fish sold at two inches in a shop may reach ten inches as an adult, and a species that is peaceful alone may be aggressive in a group.

Which calculator answers which question

• How many fish can my tank support? The Aquarium Stocking Calculator uses surface area and shows the old inch-per-gallon rule beside it.
• Is my tank big enough for a betta? The Betta Tank Size Calculator places a tank in a comfort tier and explains equipment and tankmates.
• How much should I feed? The Fish Feeding Calculator gives a starting amount to tune by watching your fish.
• What do I need to quarantine new fish? The Quarantine Tank Calculator estimates a tank size and an observation period.

Why surface area beats inches per gallon

The old rule of one inch of fish per gallon is easy to remember, but it ignores the things that matter. Oxygen enters aquarium water mostly at the surface, so surface area is the real limit on how much fish life a tank can support, and a tall tank and a long, shallow tank of the same volume are not equal. The rule also ignores shape, since a slim tetra and a bulky goldfish of the same length make very different amounts of waste, and it ignores the adult size of the fish, so it overstocks tanks of small fish and understocks tanks of large ones. The stocking calculator uses footprint and a waste factor, and it is still a guide, not a promise.

Betta: size and temperament

Bettas are often sold in tiny cups and bowls, but they do better in larger, heated and gently filtered tanks, where temperature and water quality stay stable. The betta calculator shows where your tank falls, from below the recommended minimum to spacious, and what that means for heater, filter and tankmates. Temperament varies from fish to fish, so a tank that suits one betta with company may not suit another.

Feed less, and watch

There is no universal feeding chart that works for every species and food. The most reliable guide in the hobby is observation: offer a small amount and watch. If it is eaten within about two minutes, that is roughly right, and anything left over is too much. Overfeeding is the bigger risk, because uneaten food rots, feeds algae and raises ammonia and nitrate. Fish can go without food for a short while far better than they can live in fouled water.

Quarantine protects the tank you already have

New fish, and sometimes plants, can carry parasites and disease. A quarantine tank does not need to be large or decorated. It needs to be easy to observe and to clean, with a sponge filter, a heater if the species needs one and places to hide. A few weeks of observation catches most common problems, such as ich and fin rot, before they reach the display tank, though some diseases take longer to show. Never move water, nets or equipment between the quarantine and display tanks without cleaning them.

Common mistakes

• Stocking by the size in the shop. Check adult size and temperament first.
• Adding fish to an uncycled tank. Ammonia and nitrite harm fish quickly.
• Adding everything at once. A new tank's bacteria need time to catch up with the waste.
• Skipping quarantine. One sick fish can affect the whole tank.
• Feeding for the fish's eyes. Fish will eat more than they need.