Do you have an empty 10 gallon aquarium laying around and wonder what you can put in it? Or do you have limited space and want something that doesn’t take up more room than a 10 to 20 gallon aquarium?
You can buy a 10 to 20 gallon aquarium fairly cheap. It is usually all the other stuff required to keep your pet healthy that can start to get expensive such as heating, lighting, substrate, caves and other decor, etc.
Many animals can be kept in a 10 gallon aquarium when they are babies, but most of them quickly outgrow it and need to be moved to a much bigger enclosure.
Definitely do tons of research on an animal that you plan on getting as a pet so you can give it the best home and keep it healthy. I have only provided brief information about each one here.
Here are some critters that can live in a 10 to 20 gallon aquarium their entire life:
Fire Bellied Toads
Fire bellied toads are awake during the day, so they are more interesting to watch. They require both water and land areas. You can keep 2 fire bellied toads in a 10 gallon. For more info check out Fire Bellied Toad Care.
The pacman frog is also known as the ornate horned frog. An adult male pacman frog can live in a 10 gallon, but if you get a female you might need to upsize the tank to 15 or 20 gallons. You only want to keep one in a tank as they will eat anything including other pacman frogs. They are extremely lazy and don’t move around very much. They like to spend their time half-buried in the substrate waiting for food to come by.
You can keep 1-2 tomato frogs in a 10-20 gallon. Males get up to 2-3 inches and females 4-5 inches long, so if you end up with females you might need the larger tank. They are nocturnal and require a terrestrial setup.
African Clawed Frog
African clawed frogs can grow up to 4-5 inches long. They are hardy and can live a long time, 20-30 years! You can keep 1 frog in a 10 gallon or 2 in a 20 gallon. They are fully aquatic so don’t need any land area and can have water up to 12 inches deep.
African Dwarf Frog
These guys are similar to the African clawed frog in appearance, but they only get to around 1-1/4 inches in size. They are completely aquatic and cannot survive long out of water. You can keep several in a 10 gallon. You can also keep them with peaceful fish such as guppies.
Poison Dart Frog
There are many species of poison dart frogs, and they come in many colors. They range in size from 0.4 to 2.4 inches. The rule of thumb is 1 frog per 10 gallons. They do best in a naturalistic vivarium. If you decide on getting poison dart frogs, do your research about the specific species you wish to get.
Fire Bellied Newt
There are two kinds of fire bellied newts, Japanese fire bellied newts and Oriental or Chinese fire bellied newts. Japanese fire bellied newts can grow to 3-1/2 to 5 inches, and you can keep 1 in a 10 gallon. Oriental fire bellied newts get up to 3-4 inches, and you can keep 2 in a 10 gallon. They are mostly aquatic, but do like to get out of the water occasionally so you should provide them with a little bit of land.
Axolotl are also known as Mexican walking fish, but they are actually a salamander. A single adult can be kept in a 20 gallon aquarium. They are entirely aquatic, so they don’t need a land area. Axolotl require colder water, ideally 60-64 degrees Fahrenheit, so you might need an aquarium chiller to keep the water cool enough.
See my Axolotl Care Guide
There are many types of fish that can be kept in 10 to 20 gallon aquariums. I’m not going to go into detail on each one here, but here are some that you can look into: Betta fish (siamese fighting fish), tetras, dwarf gourami, sparkling gourami, guppies, mollies, pygmy corydoras, dwarf rasbora.
Tarantulas make great low maintenance pets. Depending on the species and how big they get, they can be kept in enclosures smaller than 5 gallons up to 20 gallons or larger if you get a goliath birdeater tarantula. Most will be fine in a 10 gallon, but do your research on the species you wish to get. Their enclosure setup and care vary depending on whether they are terrestrial or arboreal and whether they need desert or tropical conditions.
Scorpions are a unique and low maintenance pet. They are not a pet you want to handle though. They are all venomous. Some can be lethal. The ones I would recommend for pets are more docile and have a weaker venom, similar to a bee sting, and won’t be lethal to you unless you are allergic.
Emperor scorpions are probably the most common scorpion pet. Full grown, they can reach 6-8 inches long. You can keep one in a 10 gallon aquarium. You can keep more than one together in a 20 gallon aquarium as long as they are of similar size. Emperor scorpions are a tropical species and require temperatures in the mid 80s and humidity of 60-80%.
Other tropical scorpions you can consider are Heterometrus species such as the Thai black scorpion (Heterometrus spinifer), Javanese jungle scorpion (Heterometrus javanensis), and Asian forest scorpion (Heterometrus longimanus).
The flat rock scorpion is a desert species. It is semi-aggressive and should be kept alone. They are the longest scorpion species in the world with some reaching over 8 inches in length.
There are other desert species which can be found as pets such as the desert hairy scorpion, which is more aggressive and likely to sting than the tropical species mentioned above.
Shrimp make interesting pets as they are very active and fun to watch. They are scavengers and will spend their time looking for leftover food. Be careful keeping fish with shrimp as many fish will eat them. Some easy to care for shrimp you can look into for a 10 to 20 gallon aquarium are red cherry shrimp, Amano shrimp, ghost shrimp, and grass shrimp.
Crabs are scavengers and they make unique pets. There are several species that can be kept in 10 to 20 gallon aquariums.
Vampire Crab: These guys are really cool looking. They get to about 2-1/2 inches wide. They require both land and water areas, 2/3 land and 1/3 water works well. You can keep several in a 10 gallon aquarium.
Red Clawed Crab: They get up to 1-1/2 to 3 inches wide. These crabs also require both land and water areas. They do best if their water is brackish with a specific gravity of 1.005. They are escape artists and need a secure lid. You can keep 3 crabs in a 10 gallon aquarium. Only keep one male as they will fight.
Fiddler Crab: Their setup is similar to the Red Clawed Crab above. They get up to 2 inches wide. They require both land and water areas with the water being brackish (specific gravity around 1.005). You can keep up to 4 fiddler crabs in a 10 gallon aquarium.
Halloween Moon Crab: These are really neat looking crabs. They get up to 2 to 2-1/2 inches. They are social and do best in groups. You can keep 2-3 in a 20 gallon aquarium, but if you can go bigger. They like lots of deep sand to dig in and decorations they can climb. They need 2 water bowls that they can easily access, a bowl of saltwater and a bowl of freshwater with calcium.
Western Hognose Snake
These are probably the cutest snakes ever! They are relatively small snakes. Females can grow up to 3 feet and males are much smaller, only getting up to 14-24 inches. You can house an adult in a 20 gallon aquarium.
Kenyan Sand Boa
These are relatively small snakes and are one of the smallest species of boa. Females average around 2 feet long and males 16-20 inches long. Adults can live comfortably in a 10-20 gallon aquarium.
The green anole is the only type of anole that is native to the United States. These lizards can be kept alone or in a group, with only one male per enclosure. Full grown, they reach 7-9 inches long with half of that being tail. You can keep 3-4 anole in a 20 gallon tall aquarium (they like to climb).
Pygmy chameleons are only suitable for the experienced chameleon keeper. The most common pygmy chameleons found available as pets are the bearded pygmy chameleon (or bearded leaf chameleon), spectral pygmy chameleon, and pitted pygmy chameleon. They get around 3 inches long. Unlike most other chameleons, they can be kept in an aquarium and can be kept in groups. The rule is 5 gallons per pygmy chameleon, so you can keep up to 2 in a 10 gallon aquarium or up to 4 in a 20 gallon.
Leopard geckos are originally from rocky, dry grassland, and desert areas of Pakistan, India, and Afghanistan. They get around 7-10 inches long. You can keep 2 geckos in a 20 gallon long aquarium, as long as only one is male as males will fight. They require several caves, preferably one on the hot end, one cold, and one humid.
I see on a lot of websites people saying you can keep an adult leopard gecko in a 10 gallon aquarium. I really believe that is too small and that a 20 gallon is much better. My leopard gecko is quite active, and once you add in their caves, a water bowl, and any other decor, there is just no room for all that in a 10 gallon!
Fat Tail Geckos
Fat tail geckos are from desert areas of West Africa. They get around 7-9 inches long. Their care is similar to leopard geckos, but they like it more humid. Fat tail geckos are shyer than leopard geckos.
Crested geckos are originally from New Caledonia. You can keep 1 adult in a 20 gallon aquarium. They require 60-80% humidity and are primarily tree dwellers. Adults grow to about 4 to 4-1/2 inches in body length. With their tail, they can be 8 inches long. It is common for them to drop their tails and they will then be tailless forever as they do not regenerate like other geckos.
A nano reef is a reef aquarium that is 40 gallons or less. They are better suited for experienced aquarists.
They can be more expensive, require more work keeping the water parameters correct, and require specific lighting. You have to keep the salinity, temperature, and other parameters stable. Due to their smaller size, they require water changes often and you have to worry about water evaporation (especially if you live in the desert like I do).
I used to have a 7 gallon nano reef for a few years. It was too small to keep fish, so I only kept live rocks, sand, and whatever grew on them. I loved looking in there and seeing what was growing. One day, I would love to have a 20 gallon nano reef!
I hope this helped give you some ideas on what you can keep in a 10 to 20 gallon aquarium.
Like I mentioned before, definitely do tons of research before getting an animal so you can keep it happy and healthy its entire life!