If you are just starting out, please check out our introduction guide Beginners’ guide to choosing the best fish tank. As you are getting your new aquarium set up, please see our guide Where to put an aquarium for helpful tips.
How big is a 20 gallon aquarium?
As you plan for your fish tank, you can start with the 20 gallon aquarium dimensions. This aquarium size is the most popular around as it’s small enough to fit most every home yet big enough to offer room for your fish and aquatic plants. There are 2 main types of 20 gallon fish tanks. The “regular” size and the “long” version. A 20 gallon aquarium is usually 24″ long by 12″ wide by 16″ high. A 20 gallon long fish tank is 30″ long by 12″ wide by 12″ high. The long fish tank isn’t as deep, but is wider. This makes a 20 gallon long fish tank appear bigger while given more space for your fish to spread out. Both a “tall or high” 20 gallon aquarium and a 20 gallon long aquarium weigh about the same. With water, gravel (substrate), and equipment, you are looking at about 225-250 pounds.
What size heater for 20 gallon aquarium?
A 20 gallon aquarium heater keeps the water temperature consistent. Fish in general, don’t like large swings in temperature. In colder climates, it’s a must have to keep your fish and plants healthy and happy. The formula we like is for every gallon of water, you’ll need 5 watts of heater to warm the water up 10 degrees above the room its in. Also, that you have an aquarium hood to keep the heat in and reduce evaporation. So for a 20 gallon aquarium, a heater of 100 watts could keep the fish tank at 80 degrees if the room it’s in is 70 degrees. Most freshwater fish like temperatures around 78-80 degrees. Some tropical fish from warmer climates like water temperatures above 85 degrees. Remember that placement of your aquarium can have an impact on your heater needs. For example, if it’s near a window that gets sun all day, your heater will work less since the sun warms the water during the day. On the other hand, a fish tank in a basement where with no windows might run more often. See our in depth guide on How to heat up and cool down an aquarium.
What type of light for a 20 gallon aquarium?
If you have a regular 20 gallon aquarium, a 24″ long LED light would work as that’s how long the aquarium tank is. If you have a 20 gallon long fish tank that is 30″ wide, a 30″ LED light would work well. A hood with an integrated LED light is the perfect solution. We like LED lights as most let you adjust the light output and how white (Kelvin rating) the light is. This is important as your fish and plants will be happier with light that mimics their natural habitat. For more info, please read our post Do fish need light?
How much gravel for 20 gallon aquarium?
Gravel or substrate is helpful for fish to know where the bottom is. The reflection from the bottom of the fish tank can confuse your fish. Having gravel on the bottom also looks nice. A good rule of thumb is 2 inches of substrate will work if you just have fish. This lets beneficial (good) bacteria grow. If it’s too deep, you risk having too little oxygen get down where excess fish food and waste goes. If left unattended, they can rot and cause issues for everything in your tank. If you also have live plants, they need a layer of nutrient rich substrate of about 1-2 inches underneath the 2 inch upper layer. And like all things you add to your aquarium, please wash it according to the directions on the package to remove any residues that may harm your fish or plants.
20 gallon aquarium stand
This size of fish tank is small enough that you can place it on a sturdy shelf (remember, it can weigh close to 250 pounds !) or sturdy desk. The key here is “sturdy”. A dedicated aquarium stand is ideal where you can make your aquarium match the decor in your home. There are metal stands, wood cabinets that have storage underneath (great for hiding equipment).
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20 gallon aquarium hood
We recommend a hood for your aquarium to help with temperature control and to keep your finned friends in the tank. They also help to reduce evaporation. Another side benefit is they can contain a bit of the noise from your filter and air pump. We recommend a hood with a built in LED light like this Amazon Choice from Marineland. The 24″ x 12″ is perfect for a regular size 20 gallon fish tank. The 30″ x 12″ is fits a 20 gallon long fish tank. The key features we like are that it has a day and night light mode, hinged for easy access when feeding or cleaning, and a removable front panel for easy access. Being an LED light, it is energy efficient.
20 gallon aquarium filter
Why do you need a filter for your 20 gallon tank? The fact is, your fish may not eat all the food in the tank before it settles on the bottom. Worse, after your fish eat all that food, they excrete wastes in the same water they live in. Yep, they poop and pee where they eat and live. All the excess fish food and aquarium fish waste sit on the bottom of your fish tank where they rot (decompose). As these things break down, they produce ammonia which is toxic to fish and plants. This is where a filter comes in. Along with a pump to move the water through the filter, the materials inside the filter provide an environment for beneficial (good) bacteria to grow. The bacteria consume the ammonia and make nitrite. This isn’t good for your fish either. Thankfully, other bacteria eats the nitrite and releases nitrate which is way less toxic to your fish.
This is why you need a filter. But what about the different kinds? There are different designs that offer trade offs. In tank filters have the filter media and pump all in the tank. The benefit of this is the water will reduce the sound made by the pump. The downside is when you have to do your regular maintenance on it, you have to pull everything out of the water and it can be a bit messy.
The other part of the filter is the pump. It’s a simple device that moves the water around through the tank and through the filter. Most filter/pump designs also introduce oxygen into the water by cascading the water back into the tank. One thing to watch is some pumps may be a problem for small fish. The inlet pipe where the pump takes in the water from the tank may be large enough for smaller fish to be pulled in. A quick way to remedy this is to place a piece of screen material that has holes large enough to let the water flow, but not let fish get sucked into the pump.
How big of a pump do you need for your 20 gallon tank? Pumps are rated in GPH or Gallons Per Hour. We recommend using a 4 to 1 rule which is 4 times the size of your tank. This means a 20 gallon fish tank would need at least an 80 Gallon Per Hour filter.
We created an indepth look on aquarium filters. Please read our post How to choose the best filter for your aquarium.
If this is your first aquarium, a 20 gallon aquarium kit is a great way to get started. In most cases, you have everything you need except water and fish.
Best 20 Gallon Aquarium
As avid fish tank aficionados, we have found many different items work well to keep our aquariums running well. This means our fish and plants are healthy. For our in depth guide, please see our post on Stuff that you will need to maintain an aquarium.
Best 20 Gallon Aquarium Kit
One huge benefit of a tank kit is that all the parts are put together for you. They match and should work well for getting started. The downside is that the parts are assembled to match for “typical” use. That means if you want to take your tank to the next level, a lot more fish, a lot more plants, etc., the included equipment may not meet the increased needs of your tank and it’s occupants. The good news is that you can enjoy a 20 gallon aquarium kit for a long time as long as is. As a place to start, a kit gets you going right away. As you find your fish or plants need more, it is easy to replace things like the filter or heater. We researched various offerings and the one that we like the best is the GloFish Aquarium Kit Fish Tank. It includes everything to get started. This kit features a glass tank. That’s a big deal as glass is easier to clean than acrylic. Glass doesn’t scratch as easily as an acrylic aquarium. This kit doesn’t include any gravel or substrate so remember to add that to your order to complete your aquarium setup.
Best 20 gallon glass aquarium
We really like the Aqueon Aquarium starter kit. It has a 20 gallon high (or regular/tall) tank. The low profile LED light hood has multiple openings for easy fish feeding. The kit includes a filter, submersible heater, thermometer, water conditioning sample, fish net, fish food sample, and a aquarium setup guide. Like most kits, it doesn’t include gravel (substrate) or other decorative items for your tank. That’s good because we love to decorate our tanks ourselves to match the fish and plants.
Best 20 gallon acrylic aquarium
Our top pick for an acrylic aquarium is the SeaClear Acrylic Combo set. It comes complete with an acrylic hood and light. The benefit of an acrylic aquarium tank is they are much lighter and stronger than their glass counterparts. And we’ve found that acrylic is clearer than glass, it almost seems like there is nothing between you and your fish. You can use this tank for either freshwater fish or saltwater fish. SeaClear uses invisible seams and has one of the best warranties around. SeaClear warrants their tanks to be shatterproof, crystal clear with a limited lifetime warranty against leakage.
Best 20 gallon long tank
One of the things we love about a long 20 gallon tank is you have more room to show off your fish. Your fish will enjoy it as they have more length to swim back and forth. This works really well for schooling fish. When you have a school of neon tetra fish, they gather in a part of the tank and move together. Their bright neon stripe and striking colors are really visually stunning. The tank size is different than a “regular” or “tall” 20 gallon tank but they both hold 20 gallons of water. The Aqueon Aquarium 20 Gallon Long is our top pick. It’s an all glass tank with clear or black silicon edge seams. We like black as it’s a little easier to keep clean than clear silicon. The frames are braced to support the additional length of the front and back glass panels. This is a well designed tank that will last a long time.
By choosing the best 20 gallon aquarium for your home, your pet fish will be healthier and happier. The beauty and joy your new tank will bring will make everyone in your household happy. Especially your cat. Kidding. But not really. Ask our cats. They love our aquariums but aren’t fans of the hoods as they keep them out. Thank goodness for fish tank hoods !