20 Liter Nano Aquarium with Phoenix Rasboras (10 Fish) - Peaceful Micro-School Setup

A 20-liter nano aquarium can be a perfect small planted tank - if you choose fish that remain tiny, behave peacefully, and look their best in a proper group. This predefined aquarium setup is built around one of the most eye-catching micro-schooling fish: Phoenix Rasbora (Boraras merah). With the right planting and gentle filtration, a school of phoenix rasboras creates constant movement and color without requiring a large aquarium footprint.

Why Phoenix Rasboras are a perfect choice for a 20L tank

Phoenix rasboras is a school fish. They feel safe and have good color displays if they are kept in a school, as opposed to just a few. The preset is based on 10 fish:

• satisfies the minimum group size needs of schooling behavior
• satisfies the minimum group size needs of schooling behavior
• keeps the tank plan simple (one species, one set of water and care needs)

In nano aquariums, the simpler the aquarium inhabitants, the better. For example, a school of a single species is usually more stable than a mixed school of species because they live, feed, behave, and have habitat requirements in.

The best layout for a phoenix rasbora nano aquarium

Provide your Phoenix rasboras with a tank they feel protected and calm:

• Dense plantings at the back and sides for cover
• Moss and fine-leaved plants to resemble a natural micro-habitat
• Floating plants for softening lighting effects and reducing stress
• Open front swimming space so you can actually see the school

A darker substrate (or a natural-toned sand) can make their red-orange colors really stand out. Add in a little bit of wood or leaf litter style décor if you like a more natural look. Just make sure there is enough open water for group swims.

Filtration and flow: gentle is better

In a 20L tank, water quality stability is very important; however, the strong current might keep the small fish stressed. A good nano filter must:

• provide gentle flow (not blasting the fish around)
• have sufficient biological media to maintain stability of water
• sucking in small fish (an intake cover helps here)

The idea is clean water and smooth movement, as phoenix rasboras tend to get bolder in a peaceful tank with plants.

Water stability basics (what matters most)

Nano tanks are volatile, and as such, the most significant success factor is

• cycle the tank before adding fish (ammonia and nitrite levels 0)
• maintain consistency in temperature (no sudden changes)
• do small, regular maintenance rather than large, infrequent changes

Phoenix rasboras flourish in a stable environment, and a stable environment includes a stable temperature.

Feeding Tips for Small Schooling Fish

Phoenix rasboras have very small mouths. It is important to only provide small foods and light meals:

• offer tiny granules, crushed flakes, or micro foods
• feed what they finish quickly
• avoid overfeeding - too much food = too much waste in 20L tanks.

A lightly stocked, well-fed but not overfed nano school appears to be a less problematic undertaking.

Change this preset in Virtual Aquarium

This page is a predefined template, which provides a proven template to start with. You can open this page in our Virtual Aquarium tool to:

• modify fish count with consideration given to schooling minimums
• test alternative nano schools (embers, chili rasboras, etc.)
• instantly see updated required water volume
• view a combined suitable temperature range for your selected fish

If you want to add additional fish types (especially bottom dwellers), you’ll usually get a more stable result by increasing the aquarium size. For a true 20L nano, a single strong school—like 10 Phoenix Rasboras—is one of the cleanest and best-looking setups you can build.