Your first aquarium: a step-by-step beginner's guide

The classic beginner's mistake is rushing. At least 3–4 weeks should pass between buying the aquarium and adding the first fish. During this time bacteria establish themselves in the filter and substrate — without them, fish will die of poisoning from their own waste.

This guide is the sequence of steps proven by thousands of aquarists. Every step is critical; you can't skip.

Step 1. Choosing tank size

For a beginner, 60–100 L is optimal. The paradox: a smaller tank is harder than a bigger one. In 30 L any feeding or nitrate mistake becomes a disaster fast; 100 L forgives mistakes.

A rectangular shape is better than round or cube. Length matters more than height — fish swim along, not up and down.

Step 2. Equipment

The minimum you can't launch without:

• An internal or external filter that turns over 4–6 tank volumes per hour.

• A thermostatically controlled heater rated at 100 W per 100 L (in winter).

• A 6500–7000 K LED light, 0.3–0.5 W/L.

• A lid or at least a cover glass — most fish are jumpers.

Step 3. Underlayer and substrate

For a community tank with undemanding fish and plants, granular gravel of 2–5 mm in a 5–7 cm layer is enough. Rinse it until the rinse water runs clear. For demanding plants — a nutrient layer under the regular substrate.

Step 4. Starting the nitrogen cycle

Pour in water that has been left to stand (24–48 hours in an open container — chlorine evaporates) or use a conditioner. Turn on the filter and heater. The first fish will go in 3–4 weeks later, once biological balance is established.

Full details on the nitrogen cycle are in a separate article. The key point: don't add fish before the cycle finishes.

Step 5. Plants and decor

In the first week, plant some undemanding species: vallisneria, anubias, hygrophila. They help start the cycle and absorb nitrates. Driftwood and a grotto can go in right away.

Step 6. The first fish

After 3–4 weeks, add 3–4 hardy fish (guppies, zebra danios, white cloud minnows). Watch for the next 10–14 days: if all are alive and healthy, you can add the rest.

Never stock the full bioload at once. Phased stocking lets bacteria scale with the growing biomass.

If you respect the biology of cycling, an aquarium serves for decades. If you rush — fish die and money is lost.

First-week checklist

• Don't feed — there are no fish yet.

• Check temperature (24–26 °C for most tropicals).

• Every 2 days — quick test for nitrites and nitrates.

• Don't change water until the cycle is done (except for the initial top-up).