Our complete guide to nano aquariums & tanks

Over the past few years, nano aquariums have exploded into the hobby scene and have become a very popular choice as a home aquarium. The popularity can largely be linked to their exceptionally reasonable price combined with the convenience of their small size. On top of this, most nano aquariums come with everything you could possibly require to start your aquarium (i.e. a filter, light, and pump).

In this blog, we will be exploring frequently asked questions about nano tanks including what they are, how many fish can be kept in them, how to set one up, and more.

What is a nano aquarium?

A nano aquarium, as the name suggests, is a small tank that typically houses miniature inhabitants. These can be either freshwater or saltwater setups and typically include detailed miniature aquascapes such as small coral reefs. It is typical to see nano aquariums containing small fish and/or invertebrates (such as shrimp).

What is considered a nano tank?

The actual size of a nano aquarium differs depending on who you ask, but at Complete Koi & Aquatics we consider nano aquariums to range from 20 litres to 90 litres.

Generally, they come with contained areas which house small filters and pumps etc. These are specifically designed for the size of the tank, making them very efficient.

How many fish could you put in a nano tank?

As with any fish keeping, the optimum quantity of fish is largely linked to water quality and thus filtration. In nano aquariums, space for filtration is at a premium, so in these instances, size really matters.

For instance, a miniature shoal of smaller fish (between 10 and 15) such as Neon Tetras or White Cloud Mountain Minnows would be perfectly acceptable in a 50 litre aquarium. Likewise, 1 or 2 larger fish such as Goldfish would equally be suitable.

If your fish are at full size and your water parameters are acceptable (i.e. Ammonia and Nitrate at <0.25), then you are in a position to add more. In fish keeping, you will always have the greatest level of success with a degree of patience. By adding small quantities of fish at a time, you allow the bacteria living in the filter to adjust to the changes without Ammonia and Nitrite spiking.

Do nano tanks/small fish tanks need a filter?

It doesn’t matter whether it is a 20 litre aquarium or a 240 litre aquarium - ALL aquariums must have filtration. The level of filtration, however, will be closely linked to the size of an aquarium, i.e. the smaller the aquarium the smaller the filter as a rule of thumb.

In each instance, there should be biological and mechanical filtration. These are explained as follows:

Mechanical filtration removes large solids such as fish waste from the main body of aquarium water. This is generally a single sponge or series of sponges.

Biological filtration houses colonies of good bacteria (Nitrobacter and Nitrosomonas) which neutralise ammonia and nitrite toxins which are a by-product of fish waste. This often comes in the form of materials with large surface areas such as K1 media, bio-balls, or ceramic media.

As mentioned previously, one of the best features of good nano aquariums is that they come as standard with overly adequate filtration systems. These can often be upgraded by adjusting to more efficient filtration media.

Do small fish tanks need air pumps?

In tropical and/or cold-water aquariums, where the water surface is disturbed by the likes of an adjustable return nozzle, it is not essential to have an air pump. The reason being is that a gaseous exchange of oxygen occurs whenever the water surface is agitated.

Despite this, having an air pump/air stone in an aquarium (cold-water/tropical) is still a good idea in our experience, regardless of size. We consider it to be a belt and braces approach as it provides additional oxygen for your fish to breathe and also acts as back-up life support should your pump ever fail.

Marine aquariums of any size do not require conventional air pumps/air stones. In marine aquariums, the bubbling induces salt creep (external salt crystallisation caused by bubbling). It is therefore more beneficial to use powerheads and wavemakers, which are like small aquatic pumps/fans which direct water around the aquarium, thereby agitating it allowing for a gaseous exchange of oxygen. For basic reefs, the kit provided with a nano marine aquarium will often be sufficient.

How to set up a nano tank

When setting up a nano aquarium (or indeed any aquarium) it is important to check you have all of the following correctly installed as per the instructions:

Filter/Filter Media
Pump
Inputs/Outputs
Heater (if tropical or marine)
Light

Once the basic equipment has been installed and tested, it’s time to put the substrate in which can be sand, aquatic compost, or gravel. In most instances, this is then followed up by dechlorinated water, which is gently poured in to cause minimal substrate disturbance. After this, it is time to put finishing touches on your aquarium by aquascaping with rocks, plants, wood, and ornaments.

Once the water is at a suitable temperature (depending on what you’re keeping) it is then time to add a small quantity of fish, invertebrates or coral. The key here is to start with a small amount and go slowly while the aquarium is cycling. The life you put in will begin to consume food, which will then turn into waste. This will break down into the toxic compounds Ammonia and Nitrite, which will be increasingly present in the aquarium for 6-8 weeks.

During this period of time, bacteria (Nitrobacter and Nitrosomonas) will colonise in the filtration area of the aquarium. Once they reach suitable numbers, the bacteria will then process the fish waste into dissolved gases, making the water good again. Only after this cycle is complete is it a good idea to add more fish.

What to put in a nano tank: Our top 5 products

We highly recommend the following products in a nano aquarium:

Synthetic gravel – This comes pre-washed so will not cloud your water and makes maintenance much more straightforward than having finer substrate such as sand.
Low maintenance ornaments – For those looking for simpler nano aquariums, rather than detailed aquascaped aquariums, it is advisable to use aquarium ornaments that are easy to remove and clean to ensure your aquarium looks pristine at all times.
A good heater – Ensuring your aquarium remains at a consistent temperature will reduce stress on fish. Even with coldwater aquariums, it is not a bad idea to use a heater set at a low temperature to deal with nighttime dips in ambient air temperature. It is also a great idea to use these in conjunction with a basic aquarium thermometer.
Good Bacteria – Whether or not you’re going through the nitrogen cycle, adding fish or cleaning the aquarium it is always great practice to add additional liquid bacteria to the aquarium to promote water, fish and aquarium health. Our favourite aquarium bacteria is either Fluval Aquarium Cycle Biological Enhancer or Evolution Aqua Pure Aquarium Balls.
Good food – If you feed your fish well, they will grow in mass and often become more colourful. We highly recommend high protein tropical fish foods that produce little in the way of fish waste.

What to keep in a nano tank

In nano aquariums, there are several suitable species which we have tried and tested which look great:

Freshwater – Fancy goldfish such as Orandas, Blackmoors and Fantails. Given their ability to grow to a reasonable size we only really recommend 1-4 in nano aquariums depending on the size of the system.
Tropical – miniature shoaling fish such as White Cloud Mountain Minnows, Neon Tetras, Zebra Danios, Cherry Barbs, Black Phantom Tetras and Harlequin Rasboras. In each of these instances, a small shoal would be perfectly acceptable.
Tropical – Shrimp. A shrimp-only tank can be very rewarding and nano aquariums are absolutely geared up for them. It is very common for small shrimp species such as cherry shrimp to breed in nanosystems.
Tropical – Livebearers. In this instance it is better to go for smaller livebearers such as endler guppies, guppies, platys and mollies.
Marine – Small marine systems will comfortably take a small reef of soft corals, several invertebrates and a couple of damsel fish such as Clownfish. In these setups, the corals tend to be the focal point, with the fish providing some foreground movement. Marine fish can be very territorial, so it is important to provide them with enough space to reduce aggression.

Of course, there are many other species that you can mix and match in these smaller aquarium systems. In any instance, it is important you do your research prior to selecting a species to ensure they don’t grow too large, and that they’re comfortable in small systems.

How to aquascape a nano tank

Aquascaping your aquarium comes down to what species you’re keeping combined with your own personal taste. In any circumstances, the first thing you will put in is your substrate. For cold water and tropical aquariums this tends to be gravel or aquarium compost. Likewise, in marine aquariums this tends to be coral sand or coral gravel.

After this has been completed you will want to create a focal point using rocks, live/fake plants and/or ornaments, which typically tends to be towards the middle/rear of the aquarium. For tropical and cold-water aquariums, the range of ornaments available is extensive.

Likewise, varying sizes of rocks and cobbles are also available, which can be stacked up to create eye-catching pieces that fish can hide in.

In marine aquariums, it is important to use a live rock or tufa rock (porous limestone), as this has an impact on the PH which is critical in marine aquariums. Again, it is recommended to build structures towards the middle/rear of the aquarium. These types of rocks are generally very pitted, and fish will naturally find homes within the crevasses.

For nano aquariums that are suitable for corals, these can be stuck to the rock using marine putty. As corals are living animals, much like adding fish it is critical to do this slowly and steadily. Check your parameters and be aware of any adverse changes which could kill the corals.

How do you clean a small fish tank?

When cleaning a nano aquarium, or small fish tank, we recommend taking the following steps:

Invest in a low-cost kitchen sponge used exclusively in the aquarium. You should use this to wipe down the glass sides of the aquarium dislodging any algae which has adhered to the glass. In certain nano aquariums, such as the Fluval Edge where accessibility is an issue and it is difficult to fit your arm in and sponge down the sides, we would highly recommend using a magnetic cleaning pad to help with this.
Once the algae has been removed from the glass, this will normally settle in your substrate, therefore it is now time to do a substrate clean. In order to do this, you should first invest in a suitable gravel cleaning tool. When doing a gravel clean, place the head of the gravel cleaner in the water and start a siphon with the wastewater going into a bucket nearby. You should use the head of the tool to poke around in the substrate removing any solids along with around 10-15% of the aquarium water. DO NOT THROW THIS WATER AWAY.
The next step in washing your aquarium filtration involves the water previously removed from the aquarium during the gravel clean. Remove the filter sponges and/or media and add them to the bucket of soiled aquarium water. It is imperative to only ever use aquarium water for this step – NEVER FRESH TAP WATER. The biological element of the filtration is very delicate and the chlorine and heavy metals present in tap water kills off the good bacterial colonies. This will lead to poor quality which results in detrimental fish health.
Ornaments, rocks and other removable decorative parts of the aquarium can be cleaned on an ad-hoc basis (as and when they’re required). This can actually be done in aquarium water, tap water or even the dishwasher providing they’re not porous. The idea here is to remove any algae or grime stuck to them. Toothbrushes are great tools for getting into any hard to reach areas.

What’s the best nano tank?

Our favourite nano aquarium is the Edge by Fluval. This stylish, contemporary tank looks absolutely superb in any home. It comes fully loaded, with an excellent little pump/filtration system and light. The aquarium is available in two different sizes (23L and 46L) and comes in both black and white options.

It is perfectly suitable for cold water, tropical and basic marine fish (with the addition of a heater). The Edge is used by both beginners and enthusiasts and we have seen some incredible aquascaping done in these compact units.

Where to buy a nano aquarium

At Complete Koi & Aquatics we stock quality nano aquariums, a beautiful array of tropical fish and all the products you need to set up your dream tank.