40 gallon fish tanks may seem large to those new to fish keeping. But they are actually a fantastic size if you have the space. They are not too huge to maintain, but are big enough to comfortably house a range of fish whether freshwater or saltwater.
I’ve used 40 gallon tanks both as display tanks and as breeders, but knowing what to look for in the best 40 gallon fish tank can be a minefield! That’s why the team and I have done the hard work for you here.
We’ve gone through painstaking research and validation, and overall we chose the SeaClear Acrylic Aquarium Combo as the best 40 gallon fish tank!
But we’ve also covered a range of other options too. So if you want to know the best 40 gallon saltwater tank, or the best tank-only option it’s all covered here too.
Before we get into it, note that a 40 gallon aquarium can weigh around 450 lbs when fully set up. Standard furniture cannot support this so you must use a 40 gallon fish tank stand to correctly distribute the weight.
- Best Overall: SeaClear Acrylic Aquarium Combo
- Best For Saltwater: Innovative Marine Nuvo Fusion Pro 2 Series
- Premium Pick: Seaclear 46 Gallon Bowfront Acrylic Tank
- Best Tank Only: Landen 90P Rimless Low Iron Aquarium
- Best Acrylic Alternative: Clear-For-Life Acrylic Rectangle Aquarium
Best 40 Gallon Fish Tank Picks Reviewed
All of the tanks in this list have been assessed for durability, clarity, and build quality. We also cover what to look for when it comes to lighting, filtration, and heating to help you find the best 40 gallon fish tank for your needs.
- Shape and Capacity: Rectangular, 40 US gallons
- Dimensions and Weight: 36.0 (l) x 15.0 (d) x 16.0 (h) inches, 20.0 pounds
- Material: Acrylic
- Equipment Included: Hood with 24 inch fluorescent light fixture (bulb not included), aquarium reflector, choice of clear, black, or cobalt blue rear panel
- Best for: Overall
The 40 gallon SeaClear Acrylic Combo set offers awesome value for an acrylic aquarium of this size and is suitable for a freshwater or marine set up.
Weighing just 20 lbs it is easy to move and position when initially setting up. And the seamless construction and ultra clear acrylic give a perfect view of your fish from every angle! You can also choose from a clear, black, or cobalt blue backing to really give your tank the wow factor.
As well as being 17 times stronger than glass, making it suitable if you are concerned about knocks from kids or pets, we also found the water temperature stayed warmer for longer. This is due to the higher heat retention of the acrylic.
Although this tank only comes with a fluorescent light fixture and no bulb, it’s quite simple to fit a separate programmable LED lighting system. Overall, although this aquarium comes with limited extras it is a fantastic acrylic tank given the price.
- Shape and Capacity: Cube, 40 US gallons
- Dimensions and Weight: 23.62 (l) x 19.68 (d) x 18.89 (h) inches, 83.0 pounds
- Material: Glass
- Equipment Included: Mesh screen lid, integrated rubber leveling mat, magnetic glass cleaner, acrylic overflow wall, 200 micron filter sock, CustomCaddy filter media basket, 2 mechanical fiberball media, 0.8 ROX carbon pack, coarse GFO filter media, MightyJet 538 GPH return pump and controller with dual directional flow nozzles
- Best for: Saltwater
The Nuvo Fusion Pro 2 is a serious piece of kit for anyone looking to start a 40 gallon marine tank. It’s cube-shaped base measures 23.62 x 19.68 inches, so you can fit it in more awkward places like the corner of a room, where a regular rectangular tank wouldn’t fit.
With a filtration system of 538 gallons per hour (GPH) it can cycle all the water in your tank over 13 times per hour! This is plenty to deal with the high bioload from marine tanks. And the directional nozzles mean you can keep the flow at the top of the tank, away from your fish.
Innovative Marine also provides 3 types of filter media, including Granular Ferric Oxide (or GFO) which is highly effective at reducing phosphates to help prevent algae outbreaks. And the water level riser with emergency overflow prevents any overspill onto your floors!
- Shape and Capacity: Rectangular bowfront, 46 US gallons
- Dimensions and Weight: 36.0 (l) x 16.5 (d) x 20.0 (h) inches, 20.0 pounds
- Material: Acrylic
- Equipment Included: Hood with 24 inch fluorescent light fixture (bulb not included), aquarium reflector
- Best for: Premium Pick
At 46 gallons the SeaClear Bowfront is a stylish alternative to the standard combo version above. It comes with a premium price tag, but the bowfront design and ultra-clear acrylic give an exceptional view of your fish.
Owners of this tank praise the clarity offered by the acrylic viewing panel when compared with glass. However, people do report the top panel can be flimsy and sometimes warp. We found it was actually better to just remove the black lighting fixture and replace it with an LED strip.
Overall, like the standard combo, you are really paying for the tank itself here which is exceptionally clear and durable. So couple it with your own lighting, filter, and heater and you’ll have a high quality set up for freshwater or marine use.
- Shape and Capacity: Rectangular, 44 US gallons
- Dimensions and Weight: 35.4 (l) x 17.7 (d) x 17.7 (h) inches, 85.8 pounds
- Material: Glass
- Equipment Included: EVA material fish tank cushioning pad
- Best for: Tank only
Landen’s 90P 44 gallon rimless fish tank is the perfect option if you are looking for a stand-alone glass aquarium. The 10mm thick heavy-duty glass is incredibly tough and scratch resistant, making it a good choice if you have pets or children in the house.
Like all Landen fish tanks, the glass has high light transmittance offering 91% transparency which really does make it look like the glass is hardly there! It’s a beautiful way to display your freshwater or marine fish.
The leveling mat is a nice touch and ensures you won’t have any slips or accidents when set up too. Overall an ultra-clear aquarium, particularly given it’s made of glass, that you can customize with your own decor and equipment.
- Shape and Capacity: Rectangular, 40 US gallons
- Dimensions and Weight: 36.0 (l) x 15.0 (d) x 16.0 (h) inches, 63.0 pounds
- Material: Acrylic
- Equipment Included: Lighting hood and leveling mat
- Best for: Acrylic alternative
As an alternative tank to the SeaClear options, Clear-For-Life’s rectangular 40 gallon aquarium is a sturdy, well-built acrylic tank with plenty of scope to customize.
The top panel has cut outs for the light fixture, as well as a cut out running the length of the tank about 4 inches from the back. You can use this to install and access an overflow in which to house your filter media. You can also fit a protein skimmer here if you plan to set up a reef tank.
This is another exceptionally clear and strong acrylic tank suitable for any home environment with areas of high traffic.
What To Look For When Buying The Best 40 Gallon Fish Tank
Before you decide on which 40 gallon aquarium will best suit your needs there are several factors you should think about.
Types of 40 Gallon Fish Tanks
If you’re looking for a larger fish tank, it’s worth first considering what you want to do with the aquarium and how you want to set it up. A 40 gallon fish tank is a fantastic size if you have the space, and can be very versatile and give you plenty of stocking options.
Display Tank Or Breeder Tank?
You can set up your 40 gallon fish tank as a normal display tank, as you would have in your home or office. This would involve setting up with the right filter, heater, and other equipment, as well as suitable substrate and decor, before adding your fish.
40 gallon breeder tanks are also very popular among aquarists as they are a great size for fish to spawn in. The 40 gallon capacity of these tanks gives fish more room to establish territory when breeding. Breeder boxes can also be used to separate the new fry as they grow.
Breeder tanks tend to be shorter in height than regular 40 gallon aquariums as it’s easier to access and tend to the fish. They are also set up with functionality in mind, rather than decor. So, for example, guppy breeders often set up these tanks without substrate for easier cleaning.
Freshwater vs Saltwater
40 gallon fish tanks give plenty of space to start a freshwater or a marine aquarium. But it’s important to think through the implications of each type before you choose which to set up.
Freshwater aquariums are usually easier to manage. This is particularly true for a 40 gallon tank as the larger water volume means it’s much easier to keep water parameters stable with less water changes needed. And the chance of significant spikes in ammonia or nitrite are very low.
40 gallons is a great size for a saltwater tank too as marine fish generally need more space and to be less densely stocked. So a larger tank capacity gives you more choice of species. We do recommend that you start a marine aquarium only when you have some experience though.
Saltwater fish tend to be more expensive than freshwater fish, you tend to need more equipment, such as protein skimmers and sumps, and it’s generally harder to maintain the correct water parameters than for a freshwater tank.
Material And Weight
A standard rectangular 40 gallon fish tank is likely to measure around 36 x 17 x 17 inches. If you choose a glass tank, it’s likely to weigh somewhere between 55 to 85 lbs . And that’s before adding the water or equipment.
As well as being more common, glass tanks are often cheaper and do offer exceptional clarity when viewing your fish. They don’t tend to scratch, but can crack in extreme circumstances. So you may want to be wary with a large glass tank if you have kids or pets around.
Acrylic tanks are much lighter. So a 40 gallon fish tank with the same dimensions as above should only weigh around 20 lbs. And although they can pick up the occasional scratch, these can generally be buffed out quite easily.
Pros And Cons Of A 40 Gallon Fish Tank
A 40 gallon fish tank is a really good size for beginners and experienced aquarists alike, and there are certainly more benefits than disadvantages!
- Large viewing area: Given the main viewing pane of a rectangular 40 gallon fish tank is around 36 x 17 inches, it gives a substantial area from which to view your fish. When compared with smaller tanks it really feels like a stand out feature in your room.
- Maintenance: 40 gallons is a perfect size for easy maintenance. The larger volume means less water changes than smaller tanks, yet it is an easier size to physically reach inside and maintain than larger aquariums.
- Flexible environment: 40 gallon aquariums are a fantastic size for marine tanks as well as freshwater. While you can definitely set up saltwater aquariums in a smaller tank, a 40 gallon aquarium gives much more choice in the range of fish you can keep.
- Need enough space!: It’s really more a point of awareness than a con, but 40 gallon tanks do start to get fairly large. They are a perfect size even for beginners if you have the room but just be aware they are likely to need a floor area of around 40 x 20 inches.
Equipment For A 40 Gallon Fish Tank
40 gallon fish tanks often come with minimal or no additional equipment, but the good news is this gives you more scope to find your own with customized features. Let’s look at the equipment needed to support the best 40 gallon fish tank.
40 Gallon Aquarium Stand
Once you take your 85 lbs glass 40 gallon aquarium, fill it with 333 lbs of water , and your substrate and decor, the total weight will be around 450 lbs. This kind of weight cannot be supported by standard furniture, and you must use a dedicated 40 gallon aquarium stand.
An aquarium stand will ensure the tank is supported properly and no weakness or faults occur due to uneven pressure. There are plenty of stands in this size, along with cabinets which have the added benefit of storage space for equipment.
Filter System For A 40 Gallon Fish Tank
40 gallons is a sizable amount of water and to keep it clean and toxin free for your fish you’ll need the right filter. Firstly, you’ll need to be able to cycle all of the water at least 4 or 5 times per hour. So a filter with a flow rate of 180 to 200 gallons per hour (GPH) is ideal.
Secondly, filter type is important in a 40 gallon aquarium. External canister filters are one of the best options as they are powerful and able to deal with the higher bio-load associated with larger tanks. However, powerful internal filters with the right flow rate can also be fine.
If you intend to set up a 40 gallon breeder tank, however, it’s best to go for an external canister or hang-on-back (HOB) filter. These are much safer than internal filters when you have fry in your tank. But do still ensure any nozzles are baffled with filter sponge for extra safety.
Heater For A 40 Gallon Fish Tank
It’s very unlikely that a 40 gallon fish tank will come with a heater included. This is actually a good thing as it gives more scope to find one with the features you need. To heat a 40 gallon tank you’ll need around a 150 watt heater, and I’d recommend an adjustable instead of preset.
This is particularly important if you are setting up a breeder tank. Many fish species need warmer water for spawning, so being able to adjust the temperature is key. Features such as an auto shut-off in case your water level drops are also useful for peace of mind.
Lighting A 40 Gallon Fish Tank
Lighting can become particularly important in a 40 gallon breeder tank. Being able to set and control the intensity of the light is key when breeding many species. Guppies, for example, tend to be more sexually active at dawn .
LED and multi-color LED (MCR) lights are often programmable and even have dimmer settings, so you can set up fading lights to mimic sunset or dawn. Not only will this help with breeding, but it also helps your fish in general as it supports their normal day and night cycles.
Tank Divider Or Breeder Box
Again, if you are setting up a 40 gallon breeder tank, be aware that some species can be aggressive to one another during spawning. Guppies even eat their own fry after giving birth! To prevent this you can use a tank divider or breeding box.
Dividers allow the fish to see each other but prevent any aggression until they are ready to breed. And using a breeding box means you can keep fry in the same tank but separate them off from any aggressive fish or other danger while they grow.
Best Fish For A 40 Gallon Aquarium
A 40 gallon fish tank gives you plenty of stocking options and you can keep some really cool freshwater fish. If you opt for a peaceful community tank, glass catfish, or cory catfish are great bottom dwellers and will help by eating any algae and keeping your aquarium clean.
Zebrafish, mollies, rainbowfish, or dwarf gouramis are all good mid-level swimmers, while danios or halfbeaks can give color and interest at the top of your tank. But although 40 gallons is a good size don’t overstock. Around 15 to 20 mid-size fish is the maximum, but it does vary depending on species.
If you choose to keep a semi-aggressive tank with fish such as an angelfish, bumblebee loaches, or large gouramis like pearl gouramis, you’ll be more limited on the number you can keep. With these fish they need more space and plant cover to establish territory.
Marine tanks need to be much less densely stocked, especially if you plan to keep corals. Only around 4 to 6 fish are suitable for a 40 gallon fish tank. Tomato clownfish, neon gobies, or longfin or banggai cardinalfish are all good starting choices, but it may take more research.
Overall, an acrylic tank like the 40 gallon SeaClear Acrylic Aquarium Combo is an excellent choice for clarity and durability. Or if you are looking for a dedicated 40 gallon marine tank the Innovative Marine Nuvo Fusion Pro 2 gives you everything you need to get started!
Even though a 40 gallon fish tank may seem large for a beginner it allows you to keep a wider range of fish whilst being easier to maintain your water parameters. So whichever tank you choose, our advice would be if you have the space and budget for 40 gallons, then go for it!
We’ve answered some of the most commonly asked questions when it comes to choosing the best 40 gallon fish tank. Take a look below!
How Much Does A 40 Gallon Fish Tank Cost To Buy?
40 gallon glass tanks can cost upwards of $350 for a quality tank. Acrylic is stronger but more expensive, and can cost upwards of $500.
How Much Does A 40 Gallon Fish Tank Cost To Run?
A 40 gallon aquarium can cost around $15 per month to run, including electricity costs and maintenance . This excludes initial purchase and equipment.
How Many Fish Can I Keep In A 40 Gallon Fish Tank?
What’s The Difference Between A 40 Gallon And A 40 Gallon Breeder Tank?
Breeder tanks tend to be shallower and easier to get into to tend to fish. They are also set up to be functional rather than decorative, so substrate may not be used to make cleaning easier.