Shopping for an aquarium is one of the best things about starting off in the hobby! Your imagination gets to run wild as you start thinking about what colors, sizes, and types of fish you want to start off with.
Should you go small or large? Bow front or classic? While your tastes will vary, what all aquarists should remember to consider is how much space and weight aquariums take up. As dense as water is, it is very heavy.
And as you will see below, weight adds up a lot faster than you might realize, which can cause problems if you’re unprepared! Let’s take a look at how much aquariums weigh by size.
Empty Aquarium Weight
The following charts display the estimated weight of aquariums of a standard design typically found in pet stores. Odd sizes aren’t included however you can use this handy online Tank Weight Calculator to get estimates for custom or uncommon sizes.
Remember that these are very rough guidelines since additions like glass thickness, decorations, the substrate, filtration equipment, lighting, and the stand all add weight to your setup.
While the water volume weight doesn’t change the amount of glass used in non-standard tanks may alter the weight by a few lbs.
Here are some useful metrics to perform your own calculations:
- 1 gallon of freshwater with no salt (specific gravity 1.000) = 8.34 lbs
- To get the weight of 1 gallon of saltwater at a specific gravity of 1.025, multiply the mass of the water by the specific gravity of seawater (8.43 x 1.025 = 8.5485).
These calculations are based on glass aquariums. I didn’t take into consideration acrylic aquariums, which are polymer based rather than glass. On average, acrylic aquariums are 50-60% lighter than glass aquariums of equal dimensions when empty.
Small Aquariums
These are the sizes most often purchased by beginners as they are inexpensive, comfortable for small fish like Livebearers and Tetras, and don’t take up too much space indoors. They can be kept on sturdy desktops or tables and don’t necessarily need a separate stand.
There are some issues to keep in mind when deciding to go with a smaller tank, though. On the one hand, you have a lot less water to haul around, making water changes a breeze! On the other hand, the less water volume you have the more easily parameters like ammonia, nitrate, and temperature can fluctuate. Small aquariums tend to be problematic for beginners because a single overfeeding or dead fish can cause drastic, even fatal changes for your pets!
| Aquarium Volume | Dimensions (L x W x H) | Empty Weight | Filled with Water |
| 2.5 Gallons | 12″ x 6″ x 8″ | 3 lbs | 27 lbs |
| 5 Gallons | 16″ x 8″ x 10″ | 7 lbs | 62 lbs |
| 10 Gallon “Leader” | 20″ x 10″ x 12″ | 11 lbs | 111 lbs |
| 15 Gallons | 24″ x 12″ x 12″ | 21 lbs | 170 lbs |
| 15 Gallon “Tall” | 20″ x 10″ x 18″ | 22 lbs | 170 lbs |
Aquariums 5 gallons and under are perfect for desktops thanks to being especially light. Many of these nano-tanks even include lighting, filtration, and just about everything else you need to get started except for fish! Just remember to pay constant attention to water quality. Good nano fish tank inhabitants include Chili Rasboras, Galaxy Rasboras, Bettas, and Red Cherry Shrimp.
Medium Aquariums
I always recommend medium sized aquariums for new hobbyists. They are the optimal balance between cost and size. Not too large as to take up tons of floor space, light enough for any type of floor, and extra water volume for fish to weather water chemistry swings.
You’ll still need to buy a good power filter, heater, and other equipment to keep your fish happy. But these larger units don’t cost all that much more than what you’d pay for a smaller tank.
That said, these aquariums do weigh enough that a separate stand is essential. If you don’t want to buy one, an especially sturdy kitchen countertop or other surface can hold most medium sized tanks.
The extra space medium sized aquariums offer gives you loads of choices for stocking your community tank as well! Fish too large for 5-15 gallon tanks like Gouramis and Angelfish are excellent residents for these tanks! Saltwater enthusiasts can start looking at Dwarf Angelfish and medium sized Clownfish. Small schooling species are also a lot more comfortable as you can keep large numbers if you prefer a single kind of fish!
| Aquarium Volume | Dimensions (L x W x H) | Empty Weight | Filled with Water |
| 20 Gallon High | 24″ x 12″ x 16″ | 25 lbs | 225 lbs |
| 20 Gallon Long | 30″ x 12″ x 12″ | 25 lbs | 225 lbs |
| 25 Gallons | 24″ x 12″ x 10″ | 32 lbs | 282 lbs |
| 29 Gallons | 30″ x 12″ x 18″ | 40 lbs | 330 lbs |
| 30 Gallon Breeder | 36″ x 18″ x 12″ | 48 lbs | 384 lbs |
| 40 Gallon Long | 48″ x 12″ x 16″ | 55 lbs | 455 lbs |
| 40 Gallon Breeder | 36″ x 18″ x 16″ | 115 lbs | 458 lbs |
Large Aquariums
Large aquariums have some special considerations of their own. These aquariums typically need a stand to hold their weight unless you’ve built some sort of custom display case. In addition, they are heavy enough that you should be certain the floor can withstand them once you get past 75 gallons.
On the plus side, the number, type, and size of fish that you can choose from is practically unlimited. Predators like large Peacock Bass and Lionfish are all viable options. Or you can keep dozens of smaller community fish together in any of these tanks.
The extra water volume helps keep water chemistry very stable unless you overcrowd the aquarium or don’t provide enough filtration. However maintenance like water changes and cleaning does take significantly more time. Heavy duty canister filters are best for these tanks as they have spacious media baskets and pumps powerful enough to provide proper circulation.
| Aquarium Volume | Dimensions (L x W x H) | Empty Weight | Filled with Water |
| 50 Gallons | 36″ x 18″ x 19″ | 100 lbs | 600 lbs |
| 55 Gallons | 48″ x 13″ x 21″ | 78 lbs | 628 lbs |
| 65 Gallons | 36″ x 18″ x 24″ | 126 lbs | 772 lbs |
| 75 Gallons | 48″ x 18″ x 21″ | 140 lbs | 850 lbs |
| 90 Gallons | 48″ x 18″ x 24″ | 160 lbs | 1050 lbs |
| 125 Gallons | 72″ x 18″ x 21″ | 206 lbs | 1400 lbs |
| 150 Gallons | 72″ x 18″ x 28″ | 338 lbs | 1800 lbs |
| 180 Gallons | 72″ x 24″ x 25″ | 430 lbs | 2100 lbs |
Extra-Large Aquariums
Once you get past 180 gallons you are in the realm of custom built tanks. Anything from 200+ gallons up to the largest aquariums in the world is going to mean weeks of planning, setup, and construction.
The weight of these tanks also depends on whether you decide to use glass or acrylic, as both materials have advantages and disadvantages. Glass is scratch-resistant, much cheaper, better insulated, and very long lasting. Acrylic, on the other hand, is lightweight, easier to mold into unique forms, has better optical properties for viewing, and is very impact resistant.
What Size Aquarium is Right for Me?
Now that you know how much aquariums weigh as well as their dimensions, let’s take a look at deciding which size aquarium is right for you!
Accessory Costs
The first thing that you’ll need to consider is the other items that you’ll be buying to get your tank up and running. I’ve mentioned heaters and filters, both of which need to be more powerful for larger tanks.
But there is also your substrate and lighting to take into account. The larger the tank, the more bags of sand or gravel you’ll need. Both are also denser than water, which means they increase the filled weight of your aquarium.
When lighting your aquarium, you’ll need both longer strips to cover a larger tank as well as more power to penetrate its depths. If you’re using a breeder-style tank, you may also want to use a second light strip. Breeder aquariums are especially wide in order to provide extra floor space for fish to spawn. But a single light strip may not provide enough illumination, especially if you are keeping live plants.
Marine fish and coral keepers have additional technology that can add to the expense. Chillers, protein skimmers, UV sterilizers, refugiums, and sumps all require space and add weight to your setup.
Freshwater or Saltwater Tank?
Are you looking to keep a freshwater or saltwater tank? Both systems have their pros and cons that will determine what sort of aquarium you’ll end up buying.
Freshwater Aquarium Fish Needs
Freshwater aquariums are best for beginners because the water chemistry isn’t as demanding. Adding and maintaining a narrow salinity range can be a challenge for first-time fishkeepers. Marine fish and corals are also less flexible when it comes to sudden shifts in ammonia, and other parameters. Which often happens due to new tank syndrome.
Freshwater fish are not only hardier but also less expensive and you can keep more per volume because freshwater holds more oxygen than saltwater does. So long as your tank is well aerated, that is!
The old one inch per gallon rule is still often repeated but it’s not very helpful unless you’re only keeping small, thin fish like tetras. Your fish’s biomass is what’s most important because how much waste is created is what mostly influences your tank’s carrying capacity (also how active your fish are).
A quick look will tell you that ten 1 inch Neon Tetras will live nicely in a 10 gallon aquarium but one 10 inch Oscar is going to have problems.
| Freshwater Fish Species | Fish Length | Minimum Aquarium Size |
| Nano Fish | ½ to 1 inch | 2.5 to 5 Gallons |
| Guppies, Tetras, Bettas | 1 ½ to 3 inches | 5 to 10 Gallons |
| Angelfish, Gouramis, Goldfish | 3 to 6 inches | 20 to 40 Gallons |
| Oscars, Piranha, Plecostomus | 8 to 14 inches | 55 to 90 Gallons |
| Pacu, Arowana, Peacock Bass | 14+ inches | 125 Gallons or more |
Saltwater Aquarium Fish Needs
By volume, saltwater doesn’t hold as much oxygen as freshwater does. On average, it has 20% less dissolved oxygen compared to freshwater of the same temperature. So you can’t keep as many fish in a saltwater tank. Also, marine fish tend to be not only pricier but more sensitive than their freshwater cousins.
This is because the ocean is a much more stable environment than rivers or lakes, where plant matter, floods, and other shifts can quickly adjust water chemistry.
If you’re interested in LPS corals and SPS corals as well, you’ll need to consider their space needs. Believe it or not, corals can be quite aggressive towards each other. Despite their limited ability to move, you’ll need to give them enough space to keep more aggressive types from stinging or eating their neighbors.
Corals also require lighting ranging from moderate to strong in intensity. If you’re using a breeder style tank with LEDs or fluorescent fixtures, you’ll almost certainly need a second strip to cover the width of the tank. And deeper tanks will need even more light intensity if you have corals growing near the substrate.
| Saltwater Fish Species | Fish Length | Minimum Aquarium Size |
| Cardinalfish, Gobies, Pygmy Wrasse | 2 inches | 10 Gallons |
| Clownfish, Pygmy Angelfish | 3 to 5 inches | 20 to 40 Gallons |
| Yellow Tangs, Hawkfish, Marine Betta | 5 to 8 inches | 55 to 90 Gallons |
| Moray Eel, Large Angelfish, Large Tangs | 12+ inches | 125 gallons or more |
Conclusion
There’s truly something for everybody in this hobby. I find that each aquarium size has its charms and bigger is not always better. A mini planted aquascape or nano reef has just as much to offer as a gigantic setup full of large fish.
Just be sure you know exactly how much space you have to work with and whether your stand (or floor) can hold up indefinitely! Once you break 100 gallons you’re looking at ½ to 1 ton of weight for your floor to deal with!
