Most people's first fish tank is small, usually 5 US gallons (19 liters) or less. It is far too common that people will buy a 1 gallon, or 3 gallon, or 5 gallon tank, and then find out later they have stocked it with the wrong kind of fish, or too many fish, or a bad mix of fish. So I wanted to make a guide for how to properly keep and stock these tiny tanks.
First of all, no matter what size your tank is, you need filtration. Today, most of these tiny tanks you can buy at the chain pet stores come with a filter, but some don't. The smaller a tank is, the faster ammonia levels will rise in it, so even with a filter, regular water changes will be needed. But without a filter, the water may need to be changed multiple times a day to prevent the water from becoming toxic to the fish. If your tiny tank didn't come with a filter, a good cost-effective solution is small sponge filters. You can get a 3 pack of sponge filters rated for up to 10 gallon tanks on Amazon for around $7 US. Or you could buy a power filter from your local pet store (or online) for a bit more.
In addition to filtration, depending on what kind of fish you have, you will likely need a heater. With these tiny tank sizes, you are probably going to be stocking with tropical fish, so a heater is more likely needed than not. When getting a heater for a tiny tank, spend the extra dollar or 2 for a decent one. I have made the mistake of just buying the cheapest one the store carried, only to discover the cheap heaters do not have an auto on/off feature, and instead constantly add heat to the water. If left unattended, these cheap heaters can cook and kill fish. So spend the extra dollar or 2 for a heater that has a built in thermostat and auto on/off feature. They usually have an indicator light that shows when they are running. Also, get a tank thermometer, to make sure the heater is working correctly. Most species that can live in a tiny tank prefer temperatures between 76 and 82 degrees F (24-28 degrees C).
Now let's discuss stocking. What can you keep in a tank so small?
1 gallon (4 liters): The general consensus among fish hobbyists will be "nothing". Really, a 1 gallon tank is just too small to be used as a permanent home for any fish. Tanks and bowls this size can be used for quarantine tanks for new fish, or hospital tanks for treating sick fish, but that's about it. Yes, there are some very tiny fish that, when kept alone, have plenty of room in a 1 gallon tank, but these species of fish are generally shoaling fish and need to be kept in larger groups that a 1 gallon tank can't support. If you really love your neon tetra, you will give it 5 friends and a tank big enough for them all to live comfortably. You won't keep it all by itself in a 1 gallon tank. It is cruel to keep a shoaling fish by itself, and it oftentimes leads to illness and even death. 1 gallon is also too small for most solitary species, like bettas, as a full-grown betta can be 3-4 inches long. There are SOME animals that can live in such a small tank, such as small shrimp or snails, but that's probably not what you had in mind for your first aquarium, and even those creatures really are better suited for larger tanks. 1 gallon tanks need more water changes, probably every day, every other day at least, as the smaller the volume of water, the faster it becomes toxic from fish waste. Most of us in the hobby don't even understand why these tanks exist other than uninformed people keep buying them.
3 gallons (11-12 liters): At this size, you can keep a single fish. Bettas are probably the most popular choice for a tank this size, and with good reason. They are a solitary species, and a great pet for a dorm room, office cube, or kitchen counter. There are other, small species that will work in this size as well, but chances are if you have a 3 gallon tank you probably have a betta. This is also a good size for keeping a small population of shrimp, or snails, without any fish. Much better than 1 gallon, in that regard. Some people have reported success in keeping a betta and shrimp together in a 3 gallon, but it is not recommended. I would not advise keeping any tank mates with a betta at this tank size. Water changes in a 3 gallon tank should be performed 2-3 times a week.
5 gallons (19 liters): This is the size that fish finally start having room to swim. Although a single betta can live in a 3 gallon tank, they will be much happier in 5 gallons, and many people argue that this is actually the minimum size for a betta. At this size, you can really see your betta's personality come out. You have room to decorate the tank with ornaments and plants, and you can keep a single fish with shrimp or snail tankmates. Oftentimes, 5 gallon tanks are used as breeding tanks, or for raising fry (baby fish). This is also a good size to use as a quarantine tank, or a hospital tank, if you keep larger aquariums or need to treat slightly larger fish with medication. 5 gallons is also a good size for keeping 1 or 2 African Dwarf Frogs with no tank mates. Water changes in a 5 gallon tank should be performed once or twice a week, depending on the livestock.
10 gallons (39 liters): I know 10 gallons isn't really "tiny", but I am including it here as 10 gallon tanks are very common and just as affordable as the smaller sizes. At this size your options really open up a lot. You can put a group of small shoaling or schooling fish in a 10 gallon tank, like tetras or corydoras. Oftentimes on this website, we hear of people who have a 3 or 5 gallon tank and they keep single fish of shoaling species, such as neon tetras. And the replies are always the same "That tank is too small because you need to have at least 6 of that species". So if you want to keep a species like tetras, 10 gallons is your bare minimum because of the group size you need. If you keep a male betta in 10 gallons, you are giving him a nice, large home with lots of space, and if you use a divider you could keep 2 male bettas, one on each side. At 10 gallons, you could keep a group of all female bettas, known as a sorority, provided you have at least 5 of them but no more than 6 (5 is the minimum for a sorority, but 6 maxes out a 10 gallon tank). 10 gallons is perfect for guppies, as you need to keep 2 females for every 1 male, and they reproduce like crazy. You could also create a small community tank, as this is a good size for platys and otos and many different kinds of fish. Male bettas can be risky with tank mates, especially other fish as tank mates, but if you want to try keeping non-fish tank mates, like maybe an african dwarf frog or 2, 10 gallons would be the minimum for keeping them together. There are several species that work well in a 10 gallon tank. Just make sure you are keeping the necessary numbers of social and shoaling species, and that you aren't over-stocking. Also make sure you are keeping compatible species together. 10 gallon tanks require water changes once a week.
Fishbowls: Just don't do it. The longstanding tradition of keeping a goldfish (or a betta) in a fishbowl is so wrong, and hobbyists not only cringe at the thought, but even feel a sense of anger when they see it. Most fishbowls hold only 1 gallon or less of water, and really aren't much better than keeping a fish in a cup. Such fishbowls are better suited for business cards, or as tip jars, than for keeping fish. If you happen to have a very large fishbowl, of say 3 gallons or more, then you can consider a single fish, but you must meet the filtration and heating requirements of the fish. A small sponge filter or under gravel filter would be recommended if you have such a bowl, and lots of plants to help aid with filtration. And you will still have to change the water every 2 or 3 days at least... maybe even every day.
Vases: Again, just don't do it. This is even worse than a fish bowl. Vases don't have a very large footprint, not a lot of distance for a fish to swim. Even if they do hold a few gallons of water, it's vertical space, not horizontal space, so the water volume can actually be more of a burden on the fish. Unlike fishbowls, where if you have a large enough bowl and some type of filtration it might work, it is never under any circumstances acceptable to keep fish in a vase. The notion that you can keep a betta in the roots of a plant in a vase is disinformation on so many levels, and many people even consider it to be animal abuse. I won't even tell you how often to change the water in a vase, because plants don't really need water changes like fish do, and all you should be putting in a vase is plants.
In any case, unless you're raising fry, always make sure your tank is the appropriate size for what your fish will need as full-grown adults. Never buy a fish that is small now but grows to be large, and put it in a tiny tank thinking "I'll just buy a larger tank later when it outgrows this tank". Because later never comes, and that is how you stunt a fish's growth, which causes a whole slew of health problems, including the fish's organs outgrowing their body, and sometimes death. That cute little 2 inch iridescent shark at Walmart can't live in a 3 gallon tank, because it will grow large and fast. And that cute little goldfish you won at the fair is only tiny because it's a baby... it will grow to be the size of pond Koi.
When planning a tiny tank, be sure to account for cycling it. The smaller the tank, the harder it is to maintain water parameters, and it could take weeks longer to cycle a 1 gallon tank than it does to cycle 10 gallons. Water testing is arguably even more important in tiny tanks than it is in large tanks, as ammonia can spike easier and faster in a tiny tank. More water = toxins are more diluted. The smaller the tank, the more often you have to change the water, to keep ammonia and other toxins at minimal levels. When setting up a new aquarium, you'll oftentimes hear about how the tank should run for 4-6 weeks before adding any fish. That generally applies to larger tanks. With tiny tanks, that amount of time is increased, to 6-8 weeks. If you add fish to the tank before it finishes cycling, you will have to do water changes every day to keep the ammonia from making your fish sick, and that will make the cycle stall even longer. So, if you go out and buy a fish and a tiny tank on the same day, you can just expect that you will be changing that water every day for 2 months. To learn more about cycling, please check here, as an entire section of this website is dedicated to tank cycling.
Plants are always welcome in aquariums, but in tiny tanks they are especially appreciated, as they help aid with filtration, and also help provide your fish with a more natural environment. Plants are not a replacement for filtration, but having your tiny tank heavily planted could help save your fish's life if there's an ammonia spike while you're at school or work. Just make sure you are using appropriate plants for your tank size, lighting conditions, and livestock. Also remove any dead or decaying plants, and trim any dead leaves off of plants.
In summary, tiny tanks can be great when done right, but for the beginner it can be challenging. Pet stores generally don't offer much information on this, and are willing to sell you an inappropriately small tank and a bad mix of way too many fish on the same day. That's how you ended up with a male betta, 1 neon tetra, and 2 cory cats, and a snail in an unfiltered, unheated kritter keeper. If that's you, don't feel too bad. That doesn't make you a terrible pet parent. You did the best you could with the information (or lack of it) that you were given. The goal of this post is to show you the error of your ways, in hopes that you truly do care about the wellbeing of your pets. If you're the person I just described, talk to us. We won't judge you. We'll help you come up with better solutions. We all started somewhere. We all made mistakes. We all thought at first "if I just get a small tank, since I'm a beginner..." without realizing small tanks require more work than large tanks do. If you're a parent wanting to set up your child with their first pet, and you're considering fish because it's "not as much work as a dog or something", think again, especially if you're planning on getting them a tiny tank.
First of all, no matter what size your tank is, you need filtration. Today, most of these tiny tanks you can buy at the chain pet stores come with a filter, but some don't. The smaller a tank is, the faster ammonia levels will rise in it, so even with a filter, regular water changes will be needed. But without a filter, the water may need to be changed multiple times a day to prevent the water from becoming toxic to the fish. If your tiny tank didn't come with a filter, a good cost-effective solution is small sponge filters. You can get a 3 pack of sponge filters rated for up to 10 gallon tanks on Amazon for around $7 US. Or you could buy a power filter from your local pet store (or online) for a bit more.
In addition to filtration, depending on what kind of fish you have, you will likely need a heater. With these tiny tank sizes, you are probably going to be stocking with tropical fish, so a heater is more likely needed than not. When getting a heater for a tiny tank, spend the extra dollar or 2 for a decent one. I have made the mistake of just buying the cheapest one the store carried, only to discover the cheap heaters do not have an auto on/off feature, and instead constantly add heat to the water. If left unattended, these cheap heaters can cook and kill fish. So spend the extra dollar or 2 for a heater that has a built in thermostat and auto on/off feature. They usually have an indicator light that shows when they are running. Also, get a tank thermometer, to make sure the heater is working correctly. Most species that can live in a tiny tank prefer temperatures between 76 and 82 degrees F (24-28 degrees C).
Now let's discuss stocking. What can you keep in a tank so small?
1 gallon (4 liters): The general consensus among fish hobbyists will be "nothing". Really, a 1 gallon tank is just too small to be used as a permanent home for any fish. Tanks and bowls this size can be used for quarantine tanks for new fish, or hospital tanks for treating sick fish, but that's about it. Yes, there are some very tiny fish that, when kept alone, have plenty of room in a 1 gallon tank, but these species of fish are generally shoaling fish and need to be kept in larger groups that a 1 gallon tank can't support. If you really love your neon tetra, you will give it 5 friends and a tank big enough for them all to live comfortably. You won't keep it all by itself in a 1 gallon tank. It is cruel to keep a shoaling fish by itself, and it oftentimes leads to illness and even death. 1 gallon is also too small for most solitary species, like bettas, as a full-grown betta can be 3-4 inches long. There are SOME animals that can live in such a small tank, such as small shrimp or snails, but that's probably not what you had in mind for your first aquarium, and even those creatures really are better suited for larger tanks. 1 gallon tanks need more water changes, probably every day, every other day at least, as the smaller the volume of water, the faster it becomes toxic from fish waste. Most of us in the hobby don't even understand why these tanks exist other than uninformed people keep buying them.
3 gallons (11-12 liters): At this size, you can keep a single fish. Bettas are probably the most popular choice for a tank this size, and with good reason. They are a solitary species, and a great pet for a dorm room, office cube, or kitchen counter. There are other, small species that will work in this size as well, but chances are if you have a 3 gallon tank you probably have a betta. This is also a good size for keeping a small population of shrimp, or snails, without any fish. Much better than 1 gallon, in that regard. Some people have reported success in keeping a betta and shrimp together in a 3 gallon, but it is not recommended. I would not advise keeping any tank mates with a betta at this tank size. Water changes in a 3 gallon tank should be performed 2-3 times a week.
5 gallons (19 liters): This is the size that fish finally start having room to swim. Although a single betta can live in a 3 gallon tank, they will be much happier in 5 gallons, and many people argue that this is actually the minimum size for a betta. At this size, you can really see your betta's personality come out. You have room to decorate the tank with ornaments and plants, and you can keep a single fish with shrimp or snail tankmates. Oftentimes, 5 gallon tanks are used as breeding tanks, or for raising fry (baby fish). This is also a good size to use as a quarantine tank, or a hospital tank, if you keep larger aquariums or need to treat slightly larger fish with medication. 5 gallons is also a good size for keeping 1 or 2 African Dwarf Frogs with no tank mates. Water changes in a 5 gallon tank should be performed once or twice a week, depending on the livestock.
10 gallons (39 liters): I know 10 gallons isn't really "tiny", but I am including it here as 10 gallon tanks are very common and just as affordable as the smaller sizes. At this size your options really open up a lot. You can put a group of small shoaling or schooling fish in a 10 gallon tank, like tetras or corydoras. Oftentimes on this website, we hear of people who have a 3 or 5 gallon tank and they keep single fish of shoaling species, such as neon tetras. And the replies are always the same "That tank is too small because you need to have at least 6 of that species". So if you want to keep a species like tetras, 10 gallons is your bare minimum because of the group size you need. If you keep a male betta in 10 gallons, you are giving him a nice, large home with lots of space, and if you use a divider you could keep 2 male bettas, one on each side. At 10 gallons, you could keep a group of all female bettas, known as a sorority, provided you have at least 5 of them but no more than 6 (5 is the minimum for a sorority, but 6 maxes out a 10 gallon tank). 10 gallons is perfect for guppies, as you need to keep 2 females for every 1 male, and they reproduce like crazy. You could also create a small community tank, as this is a good size for platys and otos and many different kinds of fish. Male bettas can be risky with tank mates, especially other fish as tank mates, but if you want to try keeping non-fish tank mates, like maybe an african dwarf frog or 2, 10 gallons would be the minimum for keeping them together. There are several species that work well in a 10 gallon tank. Just make sure you are keeping the necessary numbers of social and shoaling species, and that you aren't over-stocking. Also make sure you are keeping compatible species together. 10 gallon tanks require water changes once a week.
Fishbowls: Just don't do it. The longstanding tradition of keeping a goldfish (or a betta) in a fishbowl is so wrong, and hobbyists not only cringe at the thought, but even feel a sense of anger when they see it. Most fishbowls hold only 1 gallon or less of water, and really aren't much better than keeping a fish in a cup. Such fishbowls are better suited for business cards, or as tip jars, than for keeping fish. If you happen to have a very large fishbowl, of say 3 gallons or more, then you can consider a single fish, but you must meet the filtration and heating requirements of the fish. A small sponge filter or under gravel filter would be recommended if you have such a bowl, and lots of plants to help aid with filtration. And you will still have to change the water every 2 or 3 days at least... maybe even every day.
Vases: Again, just don't do it. This is even worse than a fish bowl. Vases don't have a very large footprint, not a lot of distance for a fish to swim. Even if they do hold a few gallons of water, it's vertical space, not horizontal space, so the water volume can actually be more of a burden on the fish. Unlike fishbowls, where if you have a large enough bowl and some type of filtration it might work, it is never under any circumstances acceptable to keep fish in a vase. The notion that you can keep a betta in the roots of a plant in a vase is disinformation on so many levels, and many people even consider it to be animal abuse. I won't even tell you how often to change the water in a vase, because plants don't really need water changes like fish do, and all you should be putting in a vase is plants.
In any case, unless you're raising fry, always make sure your tank is the appropriate size for what your fish will need as full-grown adults. Never buy a fish that is small now but grows to be large, and put it in a tiny tank thinking "I'll just buy a larger tank later when it outgrows this tank". Because later never comes, and that is how you stunt a fish's growth, which causes a whole slew of health problems, including the fish's organs outgrowing their body, and sometimes death. That cute little 2 inch iridescent shark at Walmart can't live in a 3 gallon tank, because it will grow large and fast. And that cute little goldfish you won at the fair is only tiny because it's a baby... it will grow to be the size of pond Koi.
When planning a tiny tank, be sure to account for cycling it. The smaller the tank, the harder it is to maintain water parameters, and it could take weeks longer to cycle a 1 gallon tank than it does to cycle 10 gallons. Water testing is arguably even more important in tiny tanks than it is in large tanks, as ammonia can spike easier and faster in a tiny tank. More water = toxins are more diluted. The smaller the tank, the more often you have to change the water, to keep ammonia and other toxins at minimal levels. When setting up a new aquarium, you'll oftentimes hear about how the tank should run for 4-6 weeks before adding any fish. That generally applies to larger tanks. With tiny tanks, that amount of time is increased, to 6-8 weeks. If you add fish to the tank before it finishes cycling, you will have to do water changes every day to keep the ammonia from making your fish sick, and that will make the cycle stall even longer. So, if you go out and buy a fish and a tiny tank on the same day, you can just expect that you will be changing that water every day for 2 months. To learn more about cycling, please check here, as an entire section of this website is dedicated to tank cycling.
Plants are always welcome in aquariums, but in tiny tanks they are especially appreciated, as they help aid with filtration, and also help provide your fish with a more natural environment. Plants are not a replacement for filtration, but having your tiny tank heavily planted could help save your fish's life if there's an ammonia spike while you're at school or work. Just make sure you are using appropriate plants for your tank size, lighting conditions, and livestock. Also remove any dead or decaying plants, and trim any dead leaves off of plants.
In summary, tiny tanks can be great when done right, but for the beginner it can be challenging. Pet stores generally don't offer much information on this, and are willing to sell you an inappropriately small tank and a bad mix of way too many fish on the same day. That's how you ended up with a male betta, 1 neon tetra, and 2 cory cats, and a snail in an unfiltered, unheated kritter keeper. If that's you, don't feel too bad. That doesn't make you a terrible pet parent. You did the best you could with the information (or lack of it) that you were given. The goal of this post is to show you the error of your ways, in hopes that you truly do care about the wellbeing of your pets. If you're the person I just described, talk to us. We won't judge you. We'll help you come up with better solutions. We all started somewhere. We all made mistakes. We all thought at first "if I just get a small tank, since I'm a beginner..." without realizing small tanks require more work than large tanks do. If you're a parent wanting to set up your child with their first pet, and you're considering fish because it's "not as much work as a dog or something", think again, especially if you're planning on getting them a tiny tank.
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