Everything You Need to Know About 20-GalLon Fish Tanks

If you're ready to upgrade a standard fishbowl to an aquarium a little more spacious, a 20-gallon fish tank is the perfect place to start.

 Offering plenty of sizes to accommodate all kinds of fish but not so big that it's impossible to manage alone, plenty of home aquarium beginners start off with a 20-gallon - and many decide it's the perfect sized tank to stay at, too!

 At the same time, there are some important things you need to think about before you start off with this size aquarium.

 Below we dig a little deeper into the benefits that these 20-gallon options offer, just how many fish you'll be able to hold in this tank, and all kinds of other tips and tricks to help you make the most of your new underwater set up.

 Let's get right to it!

Marina Led 20-gallon Fish Tank

20 gallon fish tank
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Benefits Of 20-gallon Fish Tanks

The biggest (and most obvious) benefit of moving to a 20-gallon tank is the ability to hold a lot more fish than you would have in a traditional bowl.

 Sure, a goldfish bowl is perfect for a goldfish or two - or maybe a betta fish - but if you want to raise more fish (especially different kinds of fish) you're going to have to step up to a bigger underwater enclosure.

 The good news is a 20-gallon tank isn't such a monstrosity that it's going to chew up a lot of counter space or real estate in your home. It's big enough to be a real focal point of any space but still small enough to manage pretty comfortably without a lot of day-to-day upkeep, too.

Another reason a lot of people gravitate to this size tank is that it offers a lot of viewing space to check out the underwater world that you have created. You'll be able to watch your fish interact with one another and the environment you've built in a way that would be pretty tough with smaller tanks - and a lot of larger tanks, too.

 Finally, the accessories you'll need to get started with a 20-gallon aquarium are pretty basic.

 You will not have to spend a mountain of money on a specialty water filter, water heater, or an air pump and bubbler set up the way you might with larger units. You also will not waste a lot of time, energy, or money cleaning, refilling, and maintaining a tank of this size.

 It's not hard to understand why so many people getting into larger format aquariums choose 20-gallon options more often than not.

just How Big Is A 20-Gallon Fish Tank Anyway?

Mid Sized Aquariums

  • 20-Gallon Long Tank 30 inches x 12 inches x 12 inches. (225 lbs - full)
  • 20-Gallon High Tank 24 inches x 12 inches x 16 inches. (225 lbs- full)

Aquariums can come in all kinds of shapes and sizes, from your standard rectangular setup to semi-custom or completely custom configurations and everything in between.

 As a general rule, though, your average 20-gallon tank is going to measure in at 30 inches long by 12 inches wide by 12 inches tall. If it's made out of high quality glass it's going to weigh about 225 pounds when it's been filled up with water, too.

 Like we mentioned earlier, this definitely isn't the largest sized aquarium you'll find on the market right now - but it's not a tiny aquarium to add to a space, either.

 You'll need to think about where you're going to set this tank up, the furniture it's going to rest atop, and where it's physically located inside of your home - keeping it away from direct sunlight and direct heating sources as much as possible .

Tetra 20-Gallon Fish Tank

Tetra 20-Gallon Fish Tank KitTetra 20-Gallon Fish Tank Kit
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How Many Fish Can I Comfortably Fit In This Size Tank

A lot of different moving parts influence how many fish you're able to keep comfortably in a tank of this size.

 Water quality, the shape and configuration of the tank, the filtration system you've implemented, the amount of oxygen you can maintain the water on a consistent basis - all of that and more plays a role in the amount of fish you can comfortably and safely keep in your new tank.

 As a general rule, though, you can (usually) getaway with 1 inch of fish for every gallon of water you have in an aquarium.

 If your fish (fully grown) measure in at 1 inch you can keep 20 of them at once without stressing them out. If your fish measure in at 2 inches, though, you'll have to cut that in half - keeping only 10.

 In most aquariums, though, your fish aren't going to be uniform size. Some might grow to an inch long, some might grow to 3 inches long, and some might grow a whole lot longer than that.

 Think about where your fishes likely to end up as it matures when you are adding them and you'll never have to worry about over populating your tank and running out of resources that keep them happy and healthy.

What Kind Of Fish Do Best In 20-gallon Fish Tanks

It's hard to imagine any fish not really thriving inside a 20-gallon tank as long as you pay attention to the tip above, but there are some that do really well in this sized aquarium - and we highlight them below.

 Beginners will want to think about filling their new 20-gallon fish tank with:


  • Black Skirted Tetras
  • Blushing Tetras
  • Cory Catfish
  • Diamond Tetras
  • Dwarf Gourami
  • Guppies
  • Mollies
  • Neon Tetras
  • Swordtails
  • Zebra Danios

 … And that's just the tip of the iceberg!

 It's never a bad idea to talk to your local aquarium experts for help picking out the right fish for your tank and the underwater environment you've created. They'll be able to point you in the right direction and steer you clear of fish that might have struggled with the kind of setup you are going with.

Aqueon LED 20-Gallon Aquarium Kit

Aqueon LED Aquarium KitAqueon LED Aquarium Kit
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  Important Things To Consider When Setting Up Your New Tank

There are a couple of other critical things you need to consider when you're getting your new 20-gallon fish tank up and running.


 For starters, a 20-gallon tank isn't going to get filled up as quickly as a goldfish bowl - and it's not going to be ready to accommodate your fish instantly, either.

 20-gallons of water that's been perfectly calibrated for your fish to live in is going to take a little bit of time to add to your tank and to treat chemically (if necessary). You'll also need to allow time for your sand, plants, and underwater biome to come together before you start adding fish.

 That's definitely something you'll want to be established before you drop your new aquatic friends into their new home. Definitely don't try to rush things or you'll end up stressing your fish and causing all kinds of headache and hassle that could have easily been avoided with just a bit of patience.


As we mentioned above your fish are going to need a little bit of time to acclimate to their new environment.

 You'll want to be sure that the oxygen levels inside your water are picture-perfect, that the algae levels are under control, that uneaten food, fish food, and dirty sand has been removed, and that your water filters, water heaters , and water pumps are all working the way you expect them to before you add your fish.


Pumps and Filters

Your water pump and your water filter for a 20-gallon set up play huge roles in the quality of the environment that your fish are going to live in.

 Thankfully, top-tier pumps and filters designed with 20-gallon set ups in mind aren't going to break your bank account the way they might have with larger tanks. You'll be able to get quality components at decent prices, filtering out and pumping water efficiently (keeping your energy bills down) so that the water stays crystal-clear and healthy for your entire fish population.




The odds are good that your 20-gallon tank will eventually balance out at about 70 ° of water temperature (room temperature) eventually.

 But it's not a bad idea to add a water heater (especially if you have tropical fish) to get that water temperature up to between 76 ° F and 80 ° F or so as quickly as possible.

 Again, you'll be able to pick up a really high quality water heater designed with 20 gallon tanks in mind for a lot less than you spend on a water heater designed to tackle much larger tanks. This is another reason why so many people choose to stay at 20-gallon– the equipment is top-tier but does not break your bank account.


Plants, Sand and Décor


Fish love having an underwater environment to live in and explore, and adding some plants to swim around, and help clean the water, and little caves to hide in all add to the overall experience your fish will have.

 Expect to spend more on plants, sand, and underwater decor for a 20-gallon than you would have on a fishbowl, that's for sure.

 If you're going with live plants you'll want to make sure you do not overcrowd things, either, as you do not want your underwater plants competing with resources that your fish need to survive - stressing out both along the way .


Closing Thoughts


At the end of the day, getting your new 20-gallon aquarium up and running - isn't going to be the monumental task a lot of people think it's going to be.

 Armed with the inside information we highlighted above you'll be able to navigate this process pretty quickly. You'll know how many new fish you can add, what kind of accessories you need to flesh out your new tank, and what to look for in quality components to give your fish the best underwater world possible - all without spending a mountain of money along the way.

 Best of luck forward!

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