Before you start: size and location
It sounds counterintuitive, but a larger tank is actually easier for beginners than a small one. At around 100 liters (roughly 25 gallons) and up, a noticeably more stable biological balance sets in — swings in temperature and water parameters matter less than in a nano tank. A tank with a footprint of 32–48 inches has proven to be a solid starting size.
For location: a solid, level surface (no glass table, no wobbly furniture), no direct sunlight (promotes algae growth and heats the tank unpredictably), outlets within reach. Important for weight: 1 liter of water weighs 1 kg (about 8.3 lb per gallon) — a 120-liter tank quickly reaches 150–180 kg (330–400 lb) including substrate, decor, and stand. Make sure your stand or floor can support that.
Shopping list
| Category | What you need |
|---|---|
| Tank & stand | Matched to your chosen location and weight capacity |
| Filter | Internal or external filter, sized for the tank |
| Heater | Usually needed, except for pure coldwater tanks |
| Lighting | LED, matched to your planting plans |
| Substrate | Gravel, sand, or aquasoil depending on plants/stocking |
| Root substrate (optional) | Only needed for ambitious planting |
| Background & decor | Rocks, driftwood (soak first), hardscape |
| Water conditioner | Neutralizes chlorine and heavy metals in tap water |
| Starter bacteria | Optional, shortens the cycling phase |
| Water test | Drop test, app-scanned strips, or our free Water Parameter Advisor |
| Net, bucket, hose | For water changes and everyday maintenance |
The steps, in the right order
Clean and place the tank
Clean the tank and accessories with clear, hot water only — no detergents or chemicals, fish can't tolerate residue. Limescale spots can be removed with a bit of vinegar, then rinse thoroughly with clear water. Attach the background, place the tank in its final location.
Substrate heater and root substrate (if used)
A substrate heater, if you're using one, goes in first — directly on the tank bottom. Root substrate (about 1 in) follows next; it should never come into direct contact with open water later, only with plant roots.
Add the substrate
Rinse gravel or sand thoroughly until the runoff stays clear — except for active aquasoil, which is never rinsed. Slope it upward toward the back (front about 1–2 in, back about 2–4 in) — this creates visual depth and makes later aquascaping easier.
Place the equipment
Position the filter and heater, route the cables. Don't plug anything in yet — equipment shouldn't run without water. Make sure everything can be switched off together quickly later during water changes.
Place decor and hardscape
Add rocks and driftwood (pre-soaked so it doesn't float) onto the substrate. Secure or glue heavy elements — burrowing fish species can otherwise topple loosely stacked rocks.
Partially fill with water
Place a plate or shallow dish on the substrate and let water flow onto it slowly — this prevents the substrate from being stirred up. Use temperature-matched water (around 75–79°F) so plants don't experience cold shock. Fill the tank only a third to halfway at first, which makes planting much easier.
Add the plants
Trim roots lightly before planting, remove any decaying leaves. Low-growing plants go in front, taller ones in back. A good rule of thumb: plant at least 40% of the floor area — plants act as important nutrient competition against algae from day one.
Fill the rest of the way and add water conditioner
Fill the tank to about an inch below the rim. Add water conditioner per the manufacturer's instructions to neutralize chlorine and heavy metals.
Plug in the equipment
Only now plug in the filter, heater (set to 75–79°F, depending on your planned stocking), and lighting. Optionally add starter bacteria — it can noticeably shorten the cycling phase.
The cycling phase: the most important (and most often skipped) step
Now the cycling phase begins — your tank needs to build a biological balance before fish can move in. Nitrifying bacteria need to establish themselves in the filter and substrate, breaking down toxic ammonia through nitrite into far less harmful nitrate. This typically takes 2–6 weeks without starter bacteria, often shorter with them.
For detailed background on the individual readings during this phase, see our articles on Ammonia/Ammonium and Nitrite — both critical readings during cycling. Our Water Parameter Advisor can evaluate your readings directly during this phase.
Common beginner mistakes
Adding fish too early: The single most common mistake — see the cycling phase above.
Too small a tank to start with: Small water volumes swing much faster in temperature and water parameters.
Garden soil instead of proper aquasoil: Contains unfiltered organic matter and residues that can destabilize the ecosystem.
Deep-cleaning the filter right after setup: Destroys the bacterial colony that just started establishing — less often is better for biological balance.
Adding too many fish at once: Overwhelms the bacterial colony, which needs time to adapt to the added load.
Reaching for chemicals at the first sign of algae: Usually a temporary symptom of the cycling phase that resolves on its own with patience.
Adding fish
Once cycling is complete: add fish slowly and in small groups, not all at once. As a rough guideline for peaceful schooling fish, the rule of thumb is roughly 1 gallon per inch of adult fish length — but this is really just a rough starting point that varies a lot by species, social behavior, and swimming-space needs. Research the actual requirements of each species before buying.
The first few weeks
Feed lightly, change about 20–30% of the water weekly, monitor water parameters closely, and clean the filter as rarely and gently as possible. After a few weeks, the tank settles into a rhythm — from there, the routine gets noticeably easier.