A 40 gallon aquarium is a popular size, but it is important to measure the space in your home to match the perfect size with the space available. Here are 40 gallon fish tank dimensions for the most popular builds:
40 gallon fish tank dimensions charts
40 gallon fish tank dimensions chart (in inches):
|Aqueon||Breeder||36.19 inches||18.25 inches||16.94 inches||48.7 gallons|
|Top Fin||Breeder||36.5 inches||15.5 inches||17.25 inches||42.3 gallons|
|SeaClear Acrylic||Breeder||36 inches||15 inches||16 inches||37.4 gallons|
Notice that each of the three manufacturers makes their 40 gallon fish tank dimensions slightly different from the others. These variations make shopping for items like tank canopies a bit more complicated.
Note that if you use one of the widely available aquarium volume calculators, the volumes do not add up directly to 40 gallons.
40 gallon fish tank dimensions chart (in centimeters):
|Aqueon||Breeder||92.1 centimeters||46.4 centimeters||43.2 centimeters||221.4 Liters|
|Top Fin||Breeder||92.7 centimeters||39.4 centimeters||43.8 centimeters||192.3 Liters|
|SeaClear Acrylic||Breeder||91.4 centimeters||38.1 centimeters||40.6 centimeters||170 Liters|
40 gallon fish tank dimensions chart weight (in pounds):
|40 gallon fish tank weights||Empty weight||Full weight (freshwater only)||Full weight (saltwater only)||Full weight w/ 50 lbs rocks, sand & decorations||Full weight w/ decorations and stand|
|Aqueon 40 gallon fish tank||58 pounds||404 pounds||419 pounds||451 pounds||~500 pounds|
|Top Fin 40 gallon fish tank||~60 pounds*||353 pounds||366 pounds||398 pounds||~450 pounds|
|SeaClear Acrylic 40 gallon fish tank||20 pounds||310 pounds||322 pounds||354 pounds||~400 pounds|
A fully loaded 40 gallon fish tank with equipment and a stand can weigh 500 pounds or more!
|40 Gallon fish tank weights||Empty weight||Full weight (freshwater only)||Full weight (saltwater only)||Full weight w/ 22.7 kg rocks, sand & decorations||Full weight w/ decorations and stand|
|Aqueon 40 gallon fish tank||26.4 kg||183.6 kg||190.5 kg||205.0 kg||227.3 kg|
|Top Fin 40 gallon fish tank||27.3 kg||160.5 kg||166.4 kg||180.9 kg||204.5 kg|
|SeaClear Acrylic 40 gallon fish tank||9.1 kg||140.9 kg||146.4 kg||160.9 kg||181.8 kg|
The 40-gallon tank is popular because it is as wide as it is tall. It creates an optimal footprint for creating your aquascape, and the depth of the tank allows plenty of light to reach the bottom of the tank.
You can easily reach every part of the tank for cleaning and maintenance.
Cost of a 40 gallon fish tank
The non-sale list price for a 40-gallon tank is ~$110, but if you have some time to plan it out and wait to score a deal, prices typically drop as much as 50% around the big holiday shopping days at the big box retailers.
After factoring in the canopy, lights, protein skimmer, live rock, live sand, heater with a controller, circulation pump, etc., you may want to budget ~$1,000-$1250. That’s a lot of money. But figure it’s better to speak the truth here.
What is the right size heater for a 40 gallon fish tank?
The ideal heater size for a 40 gallon fish tank depends on how many degrees you need to raise the water temperature above the temperature of the air in the room. A 150-watt heater (or two 75-watt heaters) is likely the best size for most 40 gallon fish tank situations.
I strongly recommend adding an aquarium controller, like the INKBIRD, to your aquarium setup. It doubles the cost of your heater equipment, but it protects your animals and investments against a heater failure.
If you read the reviews for just about any heater brand, aquarium owners blame faulty heaters for overheating their tanks. A properly programmed controller should prevent this issue.
Best aquarium lights for a 40 gallon fish tank
The best aquarium light for a 40 gallon fish tank that will hold corals is the Radion XR15. One XR15 mounted at the recommended height above the tank is all you will need to grow brilliantly colored, healthy corals.
If the solid-gold price tag of the Radion lights frightens you, there are a few options. You could try to buy used lights from someone who exited the hobby or recently upgraded. Some aquarium stores will also sell used/refurbished equipment.
Aqua Illumination is perhaps the second most popular reef tank light. They tend to be available for a modest ~ 5-10% discount.
You can also save a lot of money by purchasing NICREW or VIPARSPECTRA brands on Amazon. The lights have less features and support. The light spectrum may not be as optimized as the premium brands, but they will deliver the most PAR for the money.
How much live sand or crushed coral for a 40 gallon fish tank?
If you want to have a sand bed, the recommended amount is between 40 and 50 pounds, to create a sand bed that is just under 1” to just over 1”. That assumes the inch of sand displaces approximately 2.65 gallons of water. Double that estimate for a 2” sand bed.
How much live rock for a 40 gallon fish tank
The recommended amount of live rock for a saltwater fish tank is 40 pounds, approximately 1 pound per gallon. That should provide enough rock to give you some options to choose from to create your ideal aquascape. Any leftovers can be broken up to be used as substrate for soft coral frags or added to the sump for additional filtration capacity and/or give a home to copepods and amphipods.
Circulation pumps, also called powerheads, are pumps placed inside the display tank that help create desirable water flow in the tank, improving oxygen levels and water conditions for corals. There are a lot of models available that will get the job done. My favorite pump for a tank this size is the Icecap 2k Gyre.
Other, less expensive pumps will work well, too, if you are watching your budget or trying to ensure the absolute best value for the money. If you are searching for less expensive brands, pay close attention to how the pump is attached to the tank and avoid models with suction cups. In my experience, the cups eventually fail and then cause damage as a result.
Filtration for 40 gallon fish tank
There are 4 types of filtration that are important for maintaining the water quality for any 40 gallon fish tank:
- Foam fractionation
Mechanical filtration involves the physical trapping of particles by passing the water through a porous filter media that catches and traps particles larger than the pores. In a 40 gallon fish tank with a sump, mechanical filtration is performed by a filter sock or socks. External canister filters or hang-on-back filters will have mechanical filtration, as well as designated areas to support chemical and biological filtration.
A great canister filter option for a 40 gallon fish tank is the Fluval 207 Canister Filter (or similar models). A recommended hang-on-back filter is the Marineland Penguin 200 GPH model.
Biological filtration is the most important. Without biological filtration, you would have 40 gallon tank that would eventually kill your fish. The good news is that biological filtration happens naturally. Bacteria will grow on, in and around the live rock and other surfaces of your tank, helping remove toxic chemicals from your tank.
Chemical filtration is generally used on an ‘as needed’ basis, to remove specific unwanted pollutants from the tank. Activated carbon is a good all purpose filter media, and Granulated Ferrous Oxide (GFO) is used to remove algae-boosting phosphates.
Foam fractionation (protein skimming)
Foam fractionation is a special type of filtration that is used in saltwater tanks as an additional step to remove biological waste. This additional water polishing step is performed by a protein skimmer.
Cheapest option (that still works well)
If you are budget conscious, you could certainly have a successful 40 gallon fish tank with soft corals either without any additional filtration besides your live rock, or with a sponge filter or two. The sponge, in a sponge filter, serves as a source of mechanical filtration, as well as a substrate where the beneficial bacteria live to help provide that important biological filtration. They are run with an inexpensive air pump and are by far the cheapest option for filter. I use sponge filters in quarantine and breeding tanks. They work great.
Best protein skimmer for 40 gallon fish tank
The ideal protein skimmer for a 40 gallon tank is going to vary based on how many fish and invertebrates you keep, as well as how much you feed them. A skimmer that is too large will only produce thin skimmate, while a model that is too small will struggle to keep up. The Reef Octopus Classic 110 Space Saver Protein Skimmer CLSC-110SS is a great option, if you have a sump. If you need a Hang-on-back style, check out the Reef Octopus BH90 Hang on Protein Skimmer.
Canopy dimensions for a 40 gallon fish tank
It is important to have a fitted lid on your 40 gallon fish tank. Many of the fish species we keep will jump out of the water when startled. Without a lid, those unfortunate fish end up on the floor and die if not found fast enough.
The two primary options are a:
- A hinged glass canopy, like the Aqueon VersaTop Model: 100129040
- A custom built (or DIY) mesh lid with plastic mesh. Steel will corrode.
Stand dimensions for a 40 gallon fish tank
The stand for a 40 gallon fish tank has to be completely level and able to support ~400 pounds of weight. The top of the stand must be wide enough to sit directly under the exact dimensions of the 40 gallon tank, which means a footprint of at least 36.25 inches x 18.25 inches for an Aqueon tank, or 36.5 inches x 15.5 inches for a Top Fin.
How many fish for a 40 gallon fish tank
A 40 gallon fish tank can be safely stocked with as many as 15 small saltwater fish. The recommended number is between 9 and 15 fish. Certain saltwater fish are not compatible with each other. Be sure to refer to the saltwater fish compatibility chart or this list here for specific saltwater fish recommendations for a 40 gallon tank.
5 great saltwater fish for a 40 gallon fish tank
A 40 gallon tank has a great footprint that will allow you to keep some interesting saltwater fish and corals. There are many options to choose from, but here are 5 great saltwater fish for a 40 gallon tank, to get you started.
- Banggai Cardinalfish
- Flame hawkfish
- Midas Blenny
For more information about the recommended fish combinations and stocking levels, check out this related article on that topic:
The best saltwater fish for a 40 gallon tank.
You can also learn more about each of these saltwater fish by reading the specific care guides for Clownfish, Banggai Cardinalfish, Flame Hawkfish, Firefish, and the Midas Blenny.
A few popular fish species NOT RECOMMENDED for the dimensions of a 40 gallon fish tank
There are several popular saltwater fish types that are not appropriate or recommended for a 40 gallon fish tank, simply because the dimensions are not suitable to care for these larger fish. If you had your heart set on one of these types of fish, you are going to need a bigger tank.
Here are a few popular fish types NOT RECOMMENDED for a 40 gallon fish tank:
- Tangs, including the Blue Tang (Dory)
- Saltwater Angelfish
Alternatives to a 40 gallon fish tank
If you want to explore other options to compare with a 40 gallon fish tank, learn more about sizes somewhat smaller and larger than the 40:
Aqueon product catalog
Top Fin product descriptions