Let’s be honest, there are countless fish that are available in this hobby, and it can get overwhelming deciding which to purchase. I have the hardest time choosing fish for my aquariums because I like different ones for different reasons. This article contains fish that I personally love and would recommend adding to a 20-gallon freshwater fish tank.
You’ll have to research stocking limitations and the compatibility of these fish. I do not recommend adding all of these fish into one fish tank. They’re not all compatible with one another, or you might need a larger fish tank to keep different species. This list simply showcases what could possibly be kept in a 20-gallon aquarium.
Cherry Barb
Cherry Barbs are fantastic additions to 20 gallon freshwater aquariums. Males add an additional pop of red, while females introduce a nice subtle, red/brown combination into the mix. For the most part, Cherry Barbs keep to themselves. Most people agree that they don’t usually bother other fish. If you choose to have a group, consider getting at least 2-3 females for each male. Males could bother females relentlessly, which is similar to what male guppies do to females. So having a larger ratio of females will help disperse the pestering. Regardless, if you’re looking for a barb for your 20 gallon fish tank, consider picking up Cherry Barbs.
Cardinal Tetra
Personally, I prefer the look of Cardinal Tetras over Neon Tetras. That horizontal red streak on the Cardinal Tetra’s belly can’t be beat. Their reds and blues balance beautifully with a well-planted aquarium, and the vibrance grows if you choose to keep them in a blackwater aquarium. Cardinal Tetras generally seem more vibrant compared to Neon Tetras. I highly recommend them for a 20-gallon aquarium because they stay relatively small, do great in groups, and have spectacular red and blue colors. If you’re looking for a centerpiece schooling fish, look no further than a Cardinal Tetra.
Celestial Pearl Danio
Just looking at a Celestial Pearl Danio should be reason enough to know why they made this list. They are gorgeous looking fish with vibrant colors and white spots throughout their bodies. Celestial Pearl Danios (CPD) are also very peaceful and great options for heavily planted fish tanks. Also known as Galaxy Rasboras, these fish have an additional perk to them. They do well in aquariums with water tempereatures ranging between 72° and 76°F. If you live in an area where the ambient temperature of the home sits in that range, you may be able to keep this fish thriving without a heater. I highly recommend checking this fish out if you’re looking for a peaceful community fish, and you can likely keep anywhere between 10 and 12 individuals in a 20 gallon aquarium.
Harlequin Rasbora
Harlequin Rasboras are probably one of my favorite schooling fish. I love the orange, white, and black colorations on their bodies. Harlequin Rasboras will really stand out in a well-planted fish tank. They also have a bulkier build to them, compared to other fish that are streamlined in appearance. These Rasboras are also fairly hardy and generally do well in community tanks. However, use caution because some aquarists do say Harlequin Rasboras can become a little nippy. Not to the same extent as Tiger Barbs, but there are reports of these fish bothering Corycats and other incredibly peaceful fish.
Neolamprologus multifasciatus
Many cichlids get enormous and/or incredibly aggressive. Luckily, there are a few species that stay small and are generally peaceful. This includes the Neolamprologus multifasciatus, also known as Multis. They are shell dwelling cichlids from Lake Tanganyika. They spend most of their days patrolling and defending their shell from other Multis. They bring a unique personality to the aquarium world that you don’t often see. It’s really fun and exciting watching them defend their space or search for a new one.
Keeping Multis is a bit different because you will more than likely devote an aquarium to them. They are often kept in a species-only aquarium. This is perfectly fine for me, because watching them fight and defend their shells all day is enough entertainment. If you’re looking for a unique experience in the freshwater world consider setting a fish tank up for Neolamprologus multifasciatus. They are hardy, fun to watch, and breed fairly easily.
Rummynose Tetra
I love the torpedo appearance of Rummynose Tetras. They look amazing in a well-planted aquarium, especially if you have a decently sized school. The black and white tail with red face gives them a very unique appearance, which stands out in a fish tank.
Rummynose Tetras are a great choice for a 20-gallon aquarium. However, I have to point out that they are incredibly sensitive. If anything goes wrong in the aquarium, they are usually the first to suffer or perish. Regardless, they’re a fantastic fish that look great in 20-gallon fish tanks. If you have a larger fish tank, and are looking for something that looks similar to Rummynose Tetras, consider checking out Denison Barbs, also known as Roseline Sharks. They grow to be a bit larger, but have a similar shape and coloration.
Bristlenose Pleco
Many plecos grow to massive sizes, but fortunately, there are a few species that remain pretty small. Bristlenose Plecos are one of those, and only grow to about 6 inches at their maximum. This makes them great candidates for a 20-gallon aquarium. They’re great at eating food at the bottom of the aquarium, and will keep up with algae for the most part. Males have showy bristles over their face, which adds to their charm when they mature. Unfortunately, females have small whiskers. If there is enough decor for them in the fish tank, these fish may disappear in the aquarium for days to weeks at a time.
Bristlenose Plecos eat algae and food that falls to the bottom of the fish tank. However, you will likely need to supplement their diet with more food. If not, they run the risk of starving in a fish tank. Algae wafers are an excellent option for Bristlenose Plecos, and some aquarists feed them cucumbers and zucchini.
Peacock Gudgeon
If you’re looking for a unique fish with striking colors, check out Peacock Gudgeons. The dominating colors on this fish include red, yellow, and blue. Peacock Gudgeons are a member of the goby family and are perfectly fine being kept in freshwater aquariums. They’re incredibly peaceful fish and only grow to about 2 inches when fully grown. Peacock Gudgeons are micro predators that do great as a pair or in groups of 6 to 8. They should easily accept dry pellet food, but being predators, I highly recommend providing them with protein-rich frozen foods as well.
Care must be taken when keeping Peacock Gudgeons. Being related to gobies, they’re known jumpers. A well-fitted lid will likely be a must because not only are they jumpers, they’re also quite skittish, which increases the likelihood of them jumping.
Clown Pleco
If you’re looking for something a little smaller than a Bristlenose Pleco and don’t care as much for the algae eating aspect of a pleco, consider checking out Clown Plecos. They max out at about 4 inches and have incredible colorations. Some people may get turned away from them because they are wood eaters and can make a mess because of their diet. I enjoy the unique behavior, and will happily deal with the mess to get a chance of hearing the crunching sounds when this fish munches on driftwood.
The key to their success is providing plenty of hiding spaces and driftwood for their diet. If you are not planning to provide both in the aquarium, don’t get this fish. They’ll graze on algae but they aren’t the algae eating powerhouses other clean up crews provide.
Killifish
There are many different species of Killifish, and their colorations, small size, and peaceful temperament make them great options for 20 gallon aquariums. They are especially eye-catching in well planted aquariums.
Killifish may also be a great option for those who enjoy changing the stocking of an aquarium often. Certain Killifish species have incredibly short lifespans. These Killifish only live for anywhere between 6 to 12 months. They often spawn to continue populating the aquarium but they may not which allows you to replace them knowing they moved on naturally instead of being sent back to the pet store.
Final Notes
This list contains the 10 Best Fish For a 20 Gallon Tank, from my perspective. This list is completely opinionated, and I know many of you have your own top 10 fish list. When formulating my list, I try to provide fish with unique characteristics, habits, and behaviors. This list is much different than my 10 Best Fish For a 10 Gallon Tank – Freshwater Edition, which I advise you check out as well. If you have your personal list of fish you’d like to contribute to this website, consider reaching out!