Generally speaking, a nano aquarium is a smaller than average aquarium. To most people, this term would encompass any aquarium under ten gallons in volume that fits easily on a desktop. Not to be confused with fish bowls, a proper nano aquarium will include filtering elements and typically feature live plants to be successful. Because these aquariums are so versatile and do not require a special stand or reinforced floor, they have become very popular amongst new aquarists. They come in all different shapes as well, often deviating from the standard rectangle box. Nano aquariums can be cube, orb, hexagon, bowfront, halfmoon, column, rimless, etc. Despite all of this appeal, there are a few things to keep in mind when trying to succeed with a nano aquarium.
To read why we discourage using small bowls, you can read our Beware of Fish Bowls blog here.
Although beginner aquarists often gravitate towards nano aquariums, they really are something of an advanced art form. Someone new to maintaining aquariums can succeed with nanos, but should be advised to expect some hiccups along the way. Put simply, the larger an aquarium is, the more forgiving it will be to issues such as overfeeding, overstocking, and poor adherence to water change schedules. This boils down to dilution; you have to feed a whole lot more to pollute a 55 gallon aquarium as opposed to a 5 gallon. A larger volume of water will also have more resistance to pH crashes and temperature swings, as it has more of this built-in buffer so to speak. It is a good idea when starting out with a nano aquarium to get in the habit of testing the water often until you get a feel for the frequency of maintenance required to keep it going. This may mean cutting back on feeding and/or doing multiple small water changes a week.
Filtration on nano aquariums can also be tricky. Unless you buy a kit with built-in 3 stage filtration, you may not be able to fit a good hang on the back or internal filter on your desired setup. Because of this “undersized” filtration, nano aquariums often cannot support a high bioload and must be stocked carefully. Small fish also tend to prefer gentler flow, so putting too strong of a filter on a tiny aquarium can be somewhat detrimental. Another consideration is if you are keeping shrimp and wish to successfully propagate them, you may need to cover intake tubes with mesh or sponges to avoid losing baby shrimp. One solution is to use a sponge filter in these setups. It is the best bang for your buck, often being less than $20 and requiring only occasional maintenance. Its flow can be adjusted and it will not “suck up” any small fish or shrimp.
Another challenge with nano aquariums is temperature regulation. For nano aquariums five to ten gallons in volume, there are usually reliable/adjustable heaters available in the 25-50 watt range. However, when you’re dealing with aquariums under five gallons, it can be tricky to keep temperatures stable. A lot of the mini tank heaters will keep small aquariums at the 80-82 degree mark, but cannot be “turned down.” This is not helpful when you’re keeping very small fish and shrimp as they prefer much cooler temperatures (think 70-75 degrees). Nano fish (fish less than an inch full grown) will quickly become skinny at higher temperatures as this speeds up their metabolism. The ideal situation for most nano aquariums is to find a room in your home that can be maintained in the low 70’s. There is such a thing as too cold, however. Cold or drafty areas with small aquariums can cause the temperature to drop too low and in turn stress fish out. This can lead to disease.
It is also worth noting that when performing large water changes (50% or more) on nano aquariums, it is very important to try to match the temperature of the water you’re adding as much as possible to the temperature of the aquarium. Adding a lot of cold water to a room temperature aquarium or worse a heated aquarium can shock the inhabitants. Speaking of which...
When envisioning your nano aquarium, you should have your heart set on fish and invertebrates that are complementary to it. This means you will want to only stock fish ~two inches or less in size as adults. Cramming bigger species into smaller tanks is not the way to succeed with nanos long-term. Thankfully, with the surge in popularity of nano aquariums recently, there has been increased availability of the appropriate sized fish, shrimp, snails, etc. There’s no shortage of options. You can even find micro crabs, plant friendly dwarf crayfish, and fully aquatic frogs to go in these setups. Another great critter to keep in nano aquariums is shrimp in the genus Neocaridina or Caridina. They can often be kept with small, peaceful species of fish and pose no threat to even the most miniscule of tankmates. Some great options for fish for nano aquariums include chili rasboras, sparkling gouramis, pygmy cories, kuhli loaches, clown killifish, daisy ricefish, ember tetras, celestial pearl danios, and endler guppies, to name a few!
When it comes to feeding many nano fish species, it is often a good idea to incorporate tiny live and frozen foods when possible. Sometimes crushed flake food can work, but some species will not adapt to that. Hatching baby brine shrimp or keeping frozen baby brine on hand is often a good idea. Daphnia and microworms also make a great live food treat for nano fish. If you are feeding shrimp, thankfully many of the pellets on the market are more than adequate. You can also supplement their diet with a gel food such as repashy. The key with any of these foods is to feed only small quantities. You may need to do this twice a day to keep your nano fish well fed and happy. If you are keeping scavengers such as shrimp, dwarf crayfish, or snails with your fish, letting a little food hit the bottom of the aquarium is not the end of the world, so long as it is consumed within an hour or so.
As mentioned earlier, live plants are often key to maintaining balance in a nano aquarium. This type of setup can be fairly low-tech, requiring no additional fertilizers or CO2 to thrive. Or, if you want a tiny jungle, you can inject CO2 and fertilize. If your focus is on the plants, you will want to stock more lightly on fish. When keeping shrimp, live plants are especially important. Shrimp will graze on mosses and other plants all day long. Fake plants, unfortunately, do not satisfy in this instance as they do not host microfauna or biofilms as readily. Ferns, mosses, anubias, and floating plants often do not require high lighting or speciality substrate and can go in almost any nano aquarium provided there is a source of light. They play a key role in taking up nutrients and keeping nitrates low, so they are especially helpful in small aquariums. You can read our blog about easy aquarium plants here.
When well thought out and executed properly, nano aquariums are truly astounding. They are a tiny slice of nature in any office or home environment. Watching a nano aquarium is often a serene experience. They can be very simple, hosting only one species of fish or only shrimp. They can also be fairly complex, with activity at all levels. As long as you are dedicated in its care and attentive to its needs, you can succeed with nano aquariums.
TFH Magazine nano tank article - https://www.tfhmagazine.com/articles/freshwater/a-big-small-change-starting-a-freshwater-nano-tank-full