If you’re curious about keeping fish and considering buying a 20-gallon aquarium, you’ve come to the right place. It’s hard to know where to start when choosing fish, and tank size is just one of the things you must consider. You must also ensure you choose the right fish for your tank and that all inhabitants get along. So, to help you out, here are five fish suitable for 20-gallon aquariums.
1. Cory Catfish Are Hardy, Ideal for Beginners
Diet: Omnivore
Size: 2.5 inches
Lifespan: 5 years
Water Temperature: 72 – 82 degrees Fahrenheit
Ideal pH: 6.5 – 7.8
First on our list is the cory catfish, also known as corydoras or cory cats. Corydoras are hardy freshwater fish that are common in pet stores and come in many different shapes and colors. These striking little creatures are peaceful, so they cohabit harmoniously with most species, especially those of a similar size and nature. You must keep them in groups of at least six; they’re a schooling fish!
Corydoras are excellent small pet fish for beginners because they are hardy and thrive in varying water conditions. That said, they need clean water and are susceptible to diseases in poor conditions. In the correct environment, cory catfish can live for over five years. Cory cats are bottom dwellers and active tank cleaners, so they help keep an aquarium clean. They will spend most of their time cleaning and foraging but enjoy inactive periods throughout the day.
2. Guppies Are Small and Colorful
Diet: Omnivore
Size: 2 inches
Lifespan: 2 years
Water Temperature: 76 – 78 degrees Fahrenheit
Ideal pH: 7+
Guppies are one of the most popular pet fish and are perfect for a 20-gallon aquarium. These distinctive little creatures come in many colors and tail shapes and are cute, entertaining, and full of personality. They are prone to obesity because they quickly learn how to beg for food.
Guppies are readily available in pet shops and are peaceful and easy to care for, making them excellent for first-time fish owners. They get on with most fish, especially cory catfish and neon tetras, but they can be territorial in overcrowded conditions. You shouldn’t keep these guys with large or aggressive species because they are an easy target. Guppies are livebearers – they give birth to baby fish rather than lay eggs, meaning they breed prolifically. If you don’t want a bunch of baby Guppies, it is better to keep same-sex groups.
3. Harlequin Rasbora Are Easy to Maintain
Diet: Omnivore
Size: 2 inches
Lifespan: up to 6 years
Water Temperature: 73 – 82 degrees Fahrenheit
Ideal pH: 6 – 7.5
The harlequin rasbora, also known as the red rasbora, is the most popular of over 60 rasbora species. They come from the rainforest rivers in Singapore, so they love having lots of live vegetation in their tank, but they also like lots of open swimming space. These vibrant little guys will brighten any fish tank with their distinctive black and orange markings. They’re not the easiest fish for beginners but are generally hardy and easy to care for. Harlequin rasboras are mid to top-dwelling and fantastic low-maintenance fish in aquariums.
Like most small fish spices, the Red Rasbora needs company to feel secure, so you should have at least six of them and provide plenty of safe spaces where they can retreat. Harlequin Rasboras are incredibly passive and non-aggressive and pair well with cory catfish, neon tetras, danios, and other rasbora species.
4. Neon Tetras Are Small and Lively
Diet: Omnivore
Size: 1.5 inches
Lifespan: more than 5 years
Water Temperature: 69 – 79 degrees Fahrenheit
Ideal pH: 7
Next on our list is the super cute and distinctive neon tetra. Neon tetras are instantly recognizable because of their bright neon blue stripe running the length of their body. They also have a shiny silver belly and a flash of red across their tail.
Neon tetras are playful mid-dwellers who love darting around plants. They are from blackwater rivers, so they appreciate lots of dark areas and dense vegetation. Tetras are hardy and good for beginners but are sensitive to water changes, so they aren’t good for new setups. You must ensure the water is stable before you introduce them.
There are many tetras to choose from – and they are a schooling species, so you need at least six. The perfect tank mates for neon tetras are cory catfish, other tetra species, and rasboras. Like the rest of the fish on our list, you mustn’t keep these little guys with large, aggressive species. Otherwise, they could end up as an easy snack!
5. Zebra Danio Thrive in Groups of Six
Diet: Omnivore
Size: 2.5 inches
Lifespan: 3 – 5 years
Water Temperature: 64 – 74 degrees Fahrenheit
Ideal pH: 6.5 – 7
When discussing the best fish for a small tank, we mustn’t forget the zebra danio. The zebra danio is commonly called a zebrafish due to its distinctive black and white stripes running lengthways across its body. They are a striking addition to any aquarium, especially ones with a dark backdrop. These fish are fantastic for small tanks and beginner fish enthusiasts. These active little guys are a favorite in aquariums and are incredibly hardy. Danios prefer neutral water and are surface dwellers but will zoom around a tank.
Zebrafish are generally passive, but they may nibble the fins of other fish occasionally. To prevent this – don’t keep them with species with flowing fins or tails, such as guppies. Danios must be in a small group of at least five or six so they can shoal, and you mustn’t keep them with large, aggressive fish. The best tank mates for zebra danios are the leopard danio, guppies, loaches, mollies, and neon tetras.
