20 Liter Nano Aquarium with Least Rasboras (10 Fish) - Tiny Schooling Fish Setup

“Micro School” comes alive with a fish that would be at home within a 20-liter nano aquarium. Such a setup is already made simple with a predefined aquarium setup that is already geared towards Least Rasboras (Boraras urophthalmoides), one of the smallest fish that is sold within the aquarium trade. Least rasboras, when housed within a appropriate group size, will make for a more visible and very enjoyable sighting.

Why Least Rasboras are perfect for a 20L nano tank

Least rasboras are schooling fish and feel most comfortable in schools. Since they are small fish, having too few means that they will tend to hide. This preset features 10 rasboras, which is important because:

• it meets the minimum recommended group size for this species
• encourages natural shoaling behavior and confident feeding
• it maintains simplicity in the tank design since all fish have similar features, habitat, and feeding patterns

For new people, this will be an advantage. Nano tanks, however, get complicated if one combines several fish yet cannot keep effective group counts.

The best aquascape for least rasboras

Least rasboras thrive in a peaceful environment with plenty of plants that make them feel safe:

• Dense plants around the back and sides to form “safe zones”
• Mosses and fine-leaved plants (great for micro-fish confidence)
• Floating plants to soften the light and reduce stress
• Open front area so the school has space to swim together

A darker substrate also makes the tiny fish stand out more. If you like naturalized aquariums, a small piece of wood and a few leafy decorations can help give it a more naturalized look for the tiny fish. Just be sure it is not too cluttered.

Filtration and flow: keep it gentle

Least rasboras are small fish that prefer calmer waters. For a 20L tank, consider a filter for clean water with minimal currents:

• gentle flow (no strong "jet-like" output)
• good biological filtration for stability
• sponge intake cover to protect micro fish

When current is gentle, especially in densely planted tanks, least rasboras have a better chance of remaining in their natural state in open areas.

The real secret in a 20L tank is water stability

Small tanks are constantly changing. The easiest way to succeed is to focus on stability:

• cycle the aquarium before adding any fish (0 ppm ammonia and nitrite)
• keep temperature consistent (avoid rapid temperature changes)
• keep a routine with small changes in water exchange every week

Since least rasboras do not grow large, they do well in an environment that is unchanging.

Feeding tips for micro fish

Least rasboras have very small mouths; thus, use appropriate food sizes:

• micro granules, crushed flakes, or fine frozen/live food
• feed small portions which they consume quickly
• avoid overfeeding because leftover food will soon turn into waste in a nano tank.

For example, in a 20-liter aquarium, one of the biggest considerations in keeping water conditions crystal clear is controlled feeding.

Customize this preset in Virtual Aquarium

This page is a ready-to-use starting point. Open it in our Virtual Aquarium tool to:

• modify the number of fish, while keeping in mind the number of minimum groups
• compare least rasboras with other nano schooling species (chili rasboras, ember tetras, etc.)
• instantly see updates on required water volume
• view a combined suitable temperature range for your selected fish

if you want to add other fish species too, you’ll generally get better results if you increase the aquarium capacity first. In a true 20L nano, a single proper school like 10 least rasboras will be one of the cleanest and most beginner-friendly aquariums you can assemble.