Guide

How many fish for a 200 litre tank?

By the Aquarium Calculator team Updated 9 October 2026

A 200-litre (about 53 US gallon) aquarium holds roughly 160 litres of real water once substrate and décor are in. That comfortably supports a community such as 12 rummy-nose tetras, 6 panda corydoras and a bristlenose pleco, or about 25 neon tetras on their own, at a healthy 70–80% of the tank's capacity.

At a glance

Outside dimensions: 39 × 16 × 20 in · 100 × 40 × 50 cm
US gallons: 52.8
UK gallons: 44.0
Litres: 200.0
Water weight (full): 200 kg / 441 lb

Gross volume of the glass box, calculated from the outside dimensions.

Start with the real water volume

A typical 200-litre tank measures 100 × 40 × 50 cm. That's 200 litres of glass box, but after a 5 cm sand bed and some rock and wood the actual water volume is closer to 162 litres. Stocking, filtration and dosing should all be based on that figure. The volume calculator works out the net volume for your exact tank and substrate depth.

The common rule of thumb, one centimetre of adult fish per litre, would suggest 160–200 cm of fish. It is a rough guide at best, because it treats a slim tetra and a heavy-bodied fish of the same length as equal, even though the heavier fish produces far more waste. Our stocking calculator instead weighs each species' bioload against the tank's volume and footprint.

Four stocking plans for a 200 litre tank

Peaceful community: 12 rummy-nose tetras, 6 panda corydoras and 1 bristlenose pleco, about 77% of capacity. Angelfish centrepiece: a pair of angelfish, 8 harlequin rasboras and 6 corydoras, also about 77%; choose rasboras rather than small neons, which adult angelfish may eat. Each plan fills the top, middle and bottom of the tank and leaves room for a few snails.

Rainbow and loach tank: 8 dwarf neon rainbowfish, 6 kuhli loaches and 6 otocinclus, around 74%. Single-species school: about 25 neon tetras on their own, roughly 75%, which looks spectacular in a planted tank. Livebearers work too, around 20 guppies, but they breed quickly, so keep males only or plan for the fry.

Fish to avoid in 200 litres

Some fish sold small outgrow a 200-litre tank. Common plecos reach 45 cm and need around 450 litres; oscars need about 300 litres; clown loaches grow to 30 cm and need groups in 450 litres or more; bala sharks need even more. Common and comet goldfish belong in ponds or very large tanks. Fancy goldfish are possible, but they're cold-water fish with a heavy bioload, so keep two or three on their own rather than in a tropical community.

Compatibility matters as much as numbers. Every species must share an overlapping temperature and pH range, schooling fish need groups of at least six, and fin-nippers such as tiger barbs don't mix with long-finned fish like angelfish and bettas. The stocking calculator flags all of these problems for your exact list.

Equipment and maintenance

At these stocking levels, the calculator recommends a filter delivering about 1,100–1,150 litres per hour of real flow, about seven turnovers an hour, which usually means a canister filter rated for 300 litres or more. A 200 W heater holds 25 °C in a typical heated room; in a cold room, use two heaters. Filled with water and a 5 cm sand bed, the tank weighs about 277 kg (611 lb), so it needs a proper aquarium stand.

Plan on changing about 25% of the water every week, roughly 40 litres, and test nitrate to fine-tune the schedule. Add fish gradually after the tank has cycled, a group at a time a week or two apart, testing ammonia and nitrite after each addition.

Check your own plan

Every tank and every fish list is different. Enter your tank's dimensions and the fish you want in the stocking calculator, which now covers 83 freshwater species. It shows the stocking level, the filtration and water changes your plan needs, and warnings about schooling, aggression and water parameters.

If you're still choosing a tank, compare sizes in the aquarium size chart on the home page, and remember that a longer tank of the same volume gives fish more swimming room and supports slightly more stock than a tall one.

Check your own tank

Enter your real dimensions to get exact figures for your setup in a few seconds.

Open the Stocking Calculator