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The Nano Tank Guide

20 February 2021

Defining a ‘nano’ tank is tricky, but a good definition might be something that holds around 30 litres (6.5 gallons) or less of water and is intended to be stocked with a selection of shrimps and plants rather than fish. Despite their small size, these tanks are not aimed at beginners, but rather at more experienced aquarists looking for something more involved. This is because their small size makes them trickier to keep than the average community tank, in particular with regard to providing good water quality and stable water chemistry.

Besides running through the basics of how a nano tank is set up and maintained, we’re also going to survey some of the species suitable for nano tanks currently available at Sims Tropical Fish. They’re located at Victoria Business Centre, Victoria Road, Burgess Hill, West Sussex, but if that isn’t convenient for where you are, they also sell their fish online. For more on this, click on the link at the end of each species entry to visit their website.

Above all else, it’s their pocket-sized dimensions that have made nano tanks so popular. Even someone living in a small flat will have space for a nano tank, a 20-litre cube tank having a footprint of just 25 x 25 cm! Of course, you’ll need a power socket somewhere nearby for the filter, heater, and light, but apart from that requirement, finding a suitable spot for a nano tank shouldn’t be hard.

Really, the main advantage of a nano tank is its small size. But because they normally contain few if any fish, they are a much better habitat for small shrimp species than regular community tanks. The variety of shrimps on sale today is remarkable, with tank-bred strains in all sorts of colours including red, blue, orange, and yellow. As well as shrimps, there are other small invertebrates available that can work well in nano tanks including snails and even crabs! It’s entirely possible to create something that looks and works like a true ecosystem in a nano tank if you approach the project with care.

So, what about the downsides? Small volumes of water are intrinsically unstable, and if this instability isn’t carefully managed, this will stress or kill the livestock. A filter will take care of water quality, while frequent water changes should minimise water chemistry variations. The use of chemical buffers to prevent pH changes may also be useful, especially if you have soft water with a low carbonate hardness. Temperature fluctuations can be a major problem with very small tanks, and it crucial the tank is placed somewhere away from direct sunlight (so never on a windowsill) and away from cold draughts.

They can be, but you need to choose your species carefully. The tank also needs to be set up correctly if plants are going to flourish.
For a start, you’ll need a plant-friendly substrate that releases nutrients at the right rate. If the water becomes too nutrient-rich too quickly, algae will become a problem, but if a substrate without any nutrients is used, plant growth is likely to be poor. There are some brands of substrate designed expressly for nano tanks (such as Nano DeponitMix) but generally most of the high-end planted tank substrates should work fine. Of course, plants that grow attached to rocks and wood, such as Java Moss, don’t care about the substrate, in which case you can use whatever you want. Smooth silica sand, for example, is inexpensive and looks good, especially once it’s aged a bit.

Lighting will be needed if you want good plant growth, with LED lamps offering the best balance between light intensity (which you want) and heat (which you don’t). LEDs are also very efficient, keeping running costs down. Some aquarists also like to use carbon dioxide fertilisation with their nano tanks. While certainly not essential, these will broaden the range of species that will do well in the tank, and when used with a tank as small as a nano, such fertilisation systems will be inexpensive and cheap to run.

Almost any small plant is a viable option in a nano tank, but some are better than others. Java Moss, for example, can do so well it takes over the tank, but Christmas Moss, Vesicularia montagnei, grows much more slowly, and has become a firm favourite among nano tank gardeners. On the other hand, the slow growing but hardy Cryptocoryne species Cryptocoryne wendtii is easily obtained and an excellent choice. With leaves that get to around 15 cm long, this plant makes a great centrepiece plant for a nano tank, thriving across a broad range of water chemistry values and not needing carbon dioxide to do well.

Three other plant species that are fairly easily obtained and widely used in nano tanks are Hemianthus callitrichoides, Pogostemon helferi and Eleocharis acicularis. These plants form dense carpets of bright green given good conditions. They will need a decent substrate and carbon dioxide fertilisation to do well, however.

By default, no. If you’re aiming for a classic nano tank, the focus needs to be shrimps and plants. It’s hard to recommend any fish species for a tank smaller than 35 litres simply because they won’t have enough swimming space, but on top of that, the extra nitrate and phosphate that results from keeping fish in the tank will make algae problems far more likely.

With this said, some aquarists have kept nano tanks of above average size with species such as Celestial Pearl Danios, Ember Tetras, Ricefish, Scarlet Badis, Clown Killifish, and other very small fish species. With the schooling species at least, aim to keep at least 6-8 specimens, and that will mean a tank of not less than 35 litres.

Bettas are sometimes proposed as residents for nano tanks, but in fact they’re a poor choice. For one thing, Bettas view small shrimps as food! On top of that, Bettas are jumpy, and if the tank has an open top and if the tank has an open top you are very likely to find them dead on the carpet at some point.

Most of the small shrimps sold in aquarium shops today are either Caridina or Neocaridina species. Of the two genera, Neocaridina probably get the nod for being the easiest to keep and breed. There’s really not much variation between the species in terms of care, but some of the tank-bred varieties may be more delicate.

In any case, the default for many aquarists are the various colour forms of Neocaridina davidi, formerly known as Neocaridina heteropoda. Wild specimens are transparent with a few reddish-brown markings, but morph with large red speckles, the Cherry Shrimp, was quickly favoured by breeders and is now farmed in immense quantities. Females get to around 2-3 cm in length and have bolder colouration, while the males are smaller and tend to have more speckled in colour. The females carry the eggs until they hatch, and the juveniles that emerge are miniature shrimps, making this species particularly easy to breed.

Cherry Shrimps are often sold by grade, with the Sakura Cherry Shrimp being among the most sought-after varieties because of its solid, intense red colouration. Whereas the lower-grade Cherry Shrimps have patchy colour and clear legs, Sakura-grade shrimps will be more or less solid red, including the legs. Other colours of Neocaridina davidi are available though. Popular varieties include the Yellow Cherry Shrimp and the Blue Cherry Shrimp, while the Jade Green and the orange Sunkist Sakura are less often seen but no more difficult to keep.

Other varieties of Neocaridina davidi display variegated colouration that makes them eagerly sought after by some aquarists. The Orange Rili variety has thick orange bands around its head and body, while the extraordinary Blue Rili has alternating turquoise blue and burgundy bands. Other examples of these banded shrimps include the Yellow Rili and Black Rili shrimps.

Do bear in mind that all these shrimps are varieties of Neocaridina davidi and will interbreed readily. The resulting shrimps will likely tend towards the mottled wild-type shrimp, so aquarists should generally keep just a single variety in the tank if they want a breeding colony of one particular colour.

The other popular shrimp species kept in nano tanks is the Bee Shrimp, Caridina cantonensis. This species is smaller than the Cherry Shrimp, with females getting to no more than 2 cm long and the males even less. They are also a bit more delicate. Water quality needs to be top-notch, with plenty of oxygen (so avoid overstocking) and unlike the adapted Cherry Shrimp, the Bee Shrimp does best in soft, slightly acidic to neutral water conditions.

The wild-type shrimp is basically colourless with a few red and brown speckles, but over the years a large number of varieties have been produced, particularly in East Asia where this shrimp has become extremely popular. The Crystal Red Bee Shrimp is probably the best-known variety of Bee Shrimp. With alternating bands of white and red, it’s a very pretty species that works best in large groups. Unlike Cherry Shrimps, the males and females look similar, apart from their adult size. The Mosura Shrimp is a more selected form with solid white body and legs and bold red markings, while the Black Tiger Shrimp features black stripes on an orange-speckled body. Hinomaru-grade Shrimps resemble high-grade Crystal Red Shrimps but have a red circle on the back.
Like Cherry Shrimps, Bee Shrimps will multiply with little encouragement. All they really need is a mature tank with plenty of the microorganisms the juveniles like to eat. Mossy plants are useful in this regard, trapping algae and small particles of food, and in doing so, culturing the rotifers and other small animals the baby shrimps eat.

The basic thing is that the tank should be mature, properly maintained, well oxygenated, and generally not contain fish. While some of the very small fish will get on fine with Cherry Shrimps at least, most fish will eat the juveniles. Since shrimps only live for a year or so, you want to establish a breeding colony so that your nano tank always has some of these colourful critters crawling about!

Another good reason not to include fish is that medicines used to treat fish are often lethal to shrimps. Copper will quickly kill them, and besides being used in fish medicines, it’s also used in some plant fertilisers, so check before use.
Shrimps require a diet that provides at calcium for their shells and also iodine to regulate their moulting cycle. As they grow, they cast off their old shell and grow a new one, and without enough iodine, this can’t happen properly. Commercial shrimp foods are available that cover both these bases.
Heavy handed use of carbon dioxide fertilisation can cause problems for shrimps, primarily because they don’t handle sudden changes in pH, but also because when carbon dioxide is dissolved in water it pushes out the dissolved oxygen. So, you will need to get the balance right between providing the carbon dioxide your plants need for healthy growth and the oxygen the shrimps need to stay alive.

This article belongs to Tropical Fish Finder and can not be reproduced without permission. Kindly written by: Neale Monks.

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