90-Gallon Aquarium: 9 Things You Should Know (For Beginners)

A lot of aquariums come in different sizes and 90-gallon tanks are among the most popular choices due to their large size.

It’s given that aquarists have a lot of questions about having a 90-gallon aquarium such as how many fish they can put inside a tank? Can their floors support a 90-gallon tank? Or how much water a 90-gallon tank can hold?

Is a 90-Gallon Tank Big?

Yes, a 90-gallon tank is big. A 90-gallon tank is a perfect choice for those who are seeking to stock a large amount of fish. Also, these are perfect for saltwater aquarium setups.

The spectrum of large tanks would range from 50-gallons to 180-gallons. Large tanks offer a ton of benefits such as more space for a larger amount of fish and a bigger space for customizability; in short, large tanks are perfect for aquarists who are looking to expand their expertise and collection in fish-keeping.

Of course, it’s not easy keeping large tanks and these do require additional care and maintenance from aquarists who are interested in getting themselves a 90-gallon tank. On that note, large tanks like the 90-gallon tank aren’t suitable for amateurs in the aquarist hobby.

In addition to 90-gallon tanks, they usually measure 48’’ x 18’’ x 24’’ (following the L x W x H pattern), their empty weight is 160 lbs., and their filled weight is 1050 lbs. Now that we’ve tackled the 90-gallon tank’s measurements and weight, this is where aquarists are curious as to whether or not their floors can support this type of load.

The weight that 90-gallon tanks carry is no joke and you need to know if your floor can handle it or if you’re going to need to reinforce your floors to support the weight of the tank. Another thing that you must take note of as well is the surrounding space of the tank.

The large 90-gallon tank must have enough room around it so that other accessories like filters (HOB or canister filters) and hoses attached to them would have space. Also, the 90-gallon tank mustn’t be placed beneath shelves since they would be exposed to damage if ever the shelves fall accidentally.

Can My Floor Support A 90-Gallon Tank?

Yes, your floor can support a 90-gallon tank, so long as it’s placed in a good structural location in your house, especially in places where you have the strongest floor, directly over top of a bearing wall or column, or areas where floor joists have a short span.

According to Badman’s Tropical Fish, aquariums that are 55-gallons to 125-gallons can be supported by most floors. So you won’t have much trouble there, however, if you still want to be sure then the best place you can place them is where your floor joists span the shortest (the shorter the span is the stronger it is).

You can look at the span of your floor joists by going to your basement. You can also opt to reinforce your floors. Do take note that you should reinforce your floors before you place the tank on the floor. Why? Well, this method would allow the joists to deflect together and share the load.

With that being said, you can also put your 90-gallon tank upstairs/on the 2nd floor of your house.

How Many Fish Can I Put In A 90-Gallon Fish Tank?

There’s no actual number on how many fish you can put in a 90-gallon tank since the number of fish in a tank would depend on what species they are and what surface area is required for a specific species of fish. Not all fish are the same, so it’s difficult to give an exact number for how many you can put in a 90-gallon tank.

Like we’ve said, not all fish are the same so that means every species of fish has different tank requirements such as surface area, temperature, oxygen level, and so on and so forth. Now, several rules have been shared in the aquarist hobby regarding how many fish you can put in a tank.

These general rules are nothing but rough estimates and most often than not, they’re prone to errors. For instance, the ever-famous one inch of fish per one gallon of water is prone to errors. You can’t apply this rule to every type of fish you’re planning to put in your 90-gallon tank.

Why? Well, a big fish like the Angelfish doesn’t have the same stocking requirements as Neon Tetras, so if you have plans on stocking them in a 90-gallon tank while applying the one-inch per gallon rule, you’ll most likely end up with unhealthy and unhappy fishes.

Not only that, larger species of fish would generate a lot more waste than usual, so you’ll need to have more space so that ammonia won’t build up as quickly as it would in a small tank. Another thing, different species of fish need a specific surface area of water for them to swim around.

Other factors that would render the one-inch per gallon rule useless would be the space that decorations, substrate, plants, and filters take up inside the tank. You simply can’t apply this rule knowing that you have a bunch of other accessories stocked inside your tank. So you need to take into consideration the amount of space your accessories take up.

If you would like to know what species of fish you can put in a 90-gallon tank, refer to the bullet list below:

Freshwater tank:

  • Catfish
  • Discus and Scalare
  • Cichlids
  • Rainbow fish
  • Gourami
  • Rainbow Snakehead
  • Rasboras
  • Five Banded barbs, tiger barbs, Odessa barbs
  • Tetra species (neon tetras, Rummy-nose tetras)
  • Black lined loach, dwarf loach

Reef/Saltwater tank:

  • Tangs
  • Cardinals
  • Clowns
  • Wrasses

How Many Clownfish Can I Put In A 90-Gallon Fish Tank?

You can only keep a pair of clownfish in a 90-gallon tank, any more than that would result in aggression between the pair of clownfish and other clownfish.

Clownfishes are complicated to have due to their nature and this is why you must be very careful when stocking them in a 90-gallon tank or any large tank for that matter.

It’s imperative that you also keep only a single species of clownfish in a tank because once two different species of clownfish are kept in the same tank it would lead to aggression.

Going back to how many clownfish you can put in a 90-gallon tank, it’s highly recommended that you stick to one pair. If you decide to keep more than a pair of clownfish, let’s say three, there’s a high possibility that the mated pair would bully other clownfish.

It’s common for a pair of clownfish to assert their dominance over weaker fish inside the tank. If the third clownfish happens to be a female, the two female clownfish will be aggressive towards one another and one might end up dying in the process. To prevent this from happening, you must stick to owning just a pair in a 90-gallon tank.

Keep in mind that the pair that you should keep inside your 90-gallon tank is one female and one male. Two females would only fight each other. If you insist on adding another clownfish inside your 90-gallon tank, make sure that it’s smaller than your dominant pair.

If you don’t want to keep a pair of clownfish that’s perfectly fine since clownfish can live in solitary without getting depressed. Clownfishes don’t need pairs but they do thrive in pairs. Take note that if you decide to keep a single clownfish in your 90-gallon tank, it would most likely become a female due to the absence of a companion.

How Much Sand For A 90-Gallon Tank?

A 90-gallon tank would need 45 lbs. for 1-inch depth and 90 lbs. for 2-inch depth.

The amount we’ve mentioned above is for the average 90-gallon tank size. Do take note that the amount of sand that you’ll be putting in your tank is entirely up to you. You may want your sand bed to be shallow or deep and that would change how much sand you’ll end up putting in your 90-gallon tank.

The easiest way to know how much sand you have to put in your tank (based on your preferences while taking into consideration other accessories in the tank such as decorations and plants) is to know what your tank inhabitants need and use a sand calculator.

How Much Water Does A 90-Gallon Aquarium Hold?

A bare 90-gallon tank would hold  90 gallons of water, however, if you would put decorations, substrate, rocks, and plants in the tank, the 90-gallon aquarium would hold at least 65 gallons of water.

How much water a 90-gallon tank would carry largely depends on what you put inside the tank. The decorations and accessories that are usually placed inside the tank, such as rocks, substrate, filters, and the like, take up space inside the tank. If you put all these inside a tank and fill it up with 90 gallons of water, the water would simply overflow.

However, if you would only put bare water inside the 90-gallon tank without putting any decorations or accessories in it, then the tank would be able to hold 90 gallons of water.

It’s common for tanks to carry fewer gallons of water (which is not equivalent to the actual tank size) due to the accessories that are placed inside the tank. So the amount of water in a 90-gallon tank would vary depending on how many decorations and accessories are inside the tank itself.

How Thick Is The Glass On A 90-Gallon Aquarium?

The thickness of the glass panes on 90-gallon tanks is usually 10mm to 12mm.

The thickness of the glass panes on 90-gallon tanks has something to do with how large the panes are times the volume of the tank. Of course, not all 90-gallon glass aquariums would have the same thickness.

First, there are different types of glass used for making the panes on tanks. There are tempered glass, annealed/standard, and low iron glass. The thickness of each type of glass would vary. For instance, tempered glass would be thinner (1.5 – 2.0mm) because it’s a lighter material compared to annealed glass.

Second, glass aquariums that have tempered bottoms would have a different thickness as well since the bottom pane is made out of a different kind of glass. Lastly, if you would DIY a tank, you have the freedom to choose whatever kind of glass you want and the thickness would vary depending on the store you’re buying from and the glass they manufacture.

90 V.S. 75-Gallon & 120-Gallon Aquarium

Have trouble deciding on which large aquarium size to go with? Read the comparison below between a 90-gallon tank and a 75-gallon tank and see which would suit your interest.

90-Gallon Aquarium


  • A 90-gallon tank would have more water volume.
  • Your viewing area is increased thanks to the size of a 90-gallon tank.
  • 90-gallon tanks provide more space.
  • You have more stocking options with 90-gallon tanks.


  • The height of the tank makes it difficult to reach into the tank and move things around.
  • Maintenance would be harder compared to a smaller tank.
  • A 90-gallon tank would be a lot pricier compared to smaller tanks.

75-Gallon Aquarium


  • The water volume of a 75-gallon tank is decent enough for a large tank.
  • 75-gallon tanks provide several stacking options.
  • Not much maintenance would be required from you.
  • 75-gallon tanks fit inside most homes.
  • It’s affordable to own a 75-gallon tank.


  • Some aquarists argue that a 75-gallon tank visually looks identical to a 55-gallon tank (which is too small for their liking, considering that a 75-gallon tank is classified under the spectrum of large tanks).
  • 75-gallon tanks are pricey because they’re large tanks.
  • Prone to overcrowding.
  • Cleaning would be a problem for 75-gallon tanks.

120-Gallon Aquarium


  • 120-gallon tanks would provide more diverse stocking options.
  • You can stock more fish with this tank size.
  • The viewing area is a tad bit bigger, to some aquarists, it’s quite noticeable.
  • 120-gallon tanks can fit most rooms.
  • Provides a lot more space for your tank inhabitants to swim around in.
  • You’ll have extra room for plants inside the tank.


  • Maintenance would be harder on a tank this large.
  • Expensive.
  • Handling 120-gallon tanks would be difficult due to their weight.
  • Reaching in would be hard because these tanks are tall.
  • The stands that come with most 120-gallon aquariums aren’t sturdy at all so you would need to purchase a separate stand that’s capable of supporting the weight of your tank.

Which Is More Preferred?

The 120-gallon tank would be the best choice among the three aquarium sizes.

According to several aquarists, the bigger the tank size the better. A larger tank would equate to more space for tank inhabitants, decorations, and plants. This would accommodate an aquarist’s desire to have a lively tank that doesn’t compromise space.

Also, a 120-gallon tank would offer more stocking options which is a big plus for this hobby. Aquarists love to have diversity in their tanks and they’re only able to do so if they have a large tank that would accommodate a wider range of different species of fish.

Granted that 120-gallon tanks would be a lot more complicated to maintain, there’s no beating the benefits that you’d get from owning one. Just remember to get a decent stand that would support the weight of this large tank and get decent filtration to keep the tank clean.

90-Gallon Aquarium

Marineland 90 Corner-Flo Rectangular Aquarium, Aqueon 90 Gallon Standard Glass Aquarium, and 90 Gallon Starfire Cube Tank are the best 90-gallon tanks in the market.

Unfortunately, there aren’t any of these tanks available on Amazon so the next best thing would be to order directly on their website. With that being said, these 90-gallon tanks are manufactured by well-known brands that have been known to provide reliable aquarium products for a long time.




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