Which fish are suitable for beginners per aquarium size?

You know what often goes wrong? Someone enthusiastically buys an aquarium, sees all those beautiful fish in the store, and… boom, everything goes into that tiny 10-liter tank at once. Spoiler alert: that usually doesn't end well. 😉 A goldfish in a bowl is like cramming a giraffe into a Fiat 500—sounds funny, but you don't want to drive in one. Let's be smart about it: which fish are actually suitable for your tank, from tiny to seriously large?

In a 20-liter nano tank, you can keep shrimp, snails, or a single betta. Around 40 liters, you can keep 6–8 guppies or neon tetras. From 60–80 liters, a school of 10–12 tetras with corydoras will fit, and at 100 liters or more, large gouramis, barbs, or a group of angelfish are a good choice. Fewer fish in a tank is better because there's less waste.

Why is the size of your aquarium so important?

That old rule of "1 cm of fish per liter" sounds convenient, but it's actually complete nonsense. Imagine: a 15 cm goldfish in a 15 liter tank... you don't want that. So what should you pay attention to?

• Adult size: Small fish often grow significantly.
• Waste production: Some fish are essentially little poop factories.
• Behavior: Schools want to be with their friends, while territorial fish need space.
• Setup: Lots of plants and a good filter system help, but don't add gallons.

Overview: suitable fish per aquarium size

Aquarium size	Examples of fish populations
10 liters (nano)	• 1 betta • or 8–10 Neocaridina shrimps + 1 nerites snail
40 liter	• 6 guppies (2 male, 4 female) + 3 corydoras • or 8 neon tetras + 1 betta*
60–80 liter	• 10 rummy nose tetras + 5 corydoras + 1 honey gourami • of 12 black neon tetras + group of shrimps
100+ liter	• 15 rasboras + 6 corydoras + 2 ramirezis • or 2 angelfish + 12 tetras + 1 group of otocinclus

*Note: A betta can be kept with tetras, but check the temperament and hiding places — a calm setup with plenty of greenery is key.

Which fish fit in a 10-liter nano aquarium?

10 liters is sweet—like a mini living room. But for most fish, it's simply too small. What is nice is a single individual or super-small inhabitants that make minimal mess. Keep it zen and go for tranquility!

• 1 betta (temporary and with frequent water changes; no tankmates).
• A cheerful group of shrimps (tip: lots of greenery and moss from the moss collection).
• 1–2 nerite snails – peaceful, useful and no baby boom in freshwater.

Which fish fit in a 60–80 liter aquarium?

This is where the real fun begins. You finally have some "breathing room" for a beautiful school and a characterful fish. Think of a dynamic middle layer, a calm substrate, and plenty of greenery. With a little moss and floating plants , everyone feels safe. Popular floating plants: Salvinia , Limnobium , and the fast-growing Elodea densa .

• A school of 10–12 tetras (black neon, rummy nose, you choose).
• 3–4 corydoras for the bottom.
• A honey gourami or a pair of small gouramis as an eye-catcher.
• Combining with shrimp is possible — but make sure they don't end up as snacks.

Which fish fit in an aquarium of 100 liters or larger?

Personal talk: Welcome to the "big boys" club. Now you can really build a stable, multi-layered mini-ecosystem: a large school, a few eye-catching plants, and a cleaning crew. Give them tall plants, some wood ( mangrove or spiderwood ), and stones like Dragon Stone or Slate for hiding places.

• Schools of 15–20 tetras or rasboras.
• Dwarf cichlids such as ramirezis or apistogrammas.
• A pair of angelfish (provided your tank is high enough).

What often goes wrong for beginners (and how do you fix it)?

• Buy everything at once → add fish in stages so your filter can grow with you.
• Nano-stocking → it's better to have fewer fish, as your water values ​​will remain more stable.
• Only looking at centimeters → behavior and adult size are much more important.
• Monsterfish in a small tank → you'll save that Oscar for a 400-liter tank. 😉

Checklist for beginners

• Know exactly how many liters your tank is.
• Check your fish's adult size and temperament.
• Choose by category (10, 40, 60–80, 100+ liters).
• Don't buy everything at once.
• Change and measure water regularly.

Conclusion: Which beginner fish are the best?

In short: the larger your tank, the more options—but every size has its ideal inhabitants. Choose wisely, keep it calm, and your fish will be much healthier (and you'll be more relaxed). Not sure? Just send me a message via WhatsApp 📲 or schedule a service , and we'll take a look at your tank together.

Read more & shop

• How to make a nano aquascape?
• The 15 best beginner plants
• These are the most well-known aquascape styles
• How do you cycle an aquarium?
• Aquarium Refresh: Step-by-Step
• Cleaning the bottom: how often?
• White haze: causes & solution
• Scum layer: what do you do about it?
• Combating green algae
• Treating blue-green algae
• All about aquarium moss
• Vallisneria: the ultimate guide
• Cardinals & Neon Tetra Guide
• Platy's & Mollies guide
• Which fish are suitable for beginners?
• Shop: all aquarium plants
• Shop: aquarium wood
• Shop: aquarium stones