So, you’ve decided you want a fish tank for your home. Great idea! Aquariums are fun, relaxing, and educational. But… which of the dozens of models should you go for? Big and bold? Or best keep it small? No worries: we’ll help you figure out the perfect tank size for you.
Below, let’s see why you shouldn’t go too small or too big—and what we think is the perfect happy medium.
Why you shouldn’t go too small
When setting up your first fish tank, it can be tempting to opt for something small. A little 2.5 or 5 gallon doesn’t take up a lot of space, and you won’t be out hundreds of dollars if you don’t end up liking being an aquarist.
However, we don’t necessarily recommend going ultra-compact (< 10 gallons). Here’s why.
Margin for error
One of the main—and most commonly overlooked—problems with an extra-small aquarium is the fact that there’s almost no margin for error. Think of it like this: the more water, the more dilution. Bigger systems are more robust and stable than small ones, and they’re much less prone to potentially deadly (to fish, anyway) nitrogen cycle swings.
In a very small tank (think 5-10 gallons), small mistakes can have big consequences for water quality. As counterintuitive as it may sound, XS fish tanks aren’t actually better for beginning aquarists—they’re worse!
Limited stocking options
One of the most common things we hear from new aquarists is “I wish I’d gone bigger”. This is partially due to the stability issues mentioned above, but the more important problem for most folks is how limiting a small tank is when it comes to the fish you can keep. Once you start getting into the hobby, aquariums that used to look huge become just… normal.
For example, what fish would we recommend for a 5-gallon aquarium? Actually, if you’re a beginner, none. A very limited number of species that can be kept in water volumes this small does exist, but the inherent instability of smaller systems means you could be in for heartbreak unless you’ve already got some experience.
To avoid having to “graduate” to increasingly larger tanks (and spending boatloads of money in the process), it can be helpful to think about which fish you’d like to keep and base the size of your aquarium on your choices, rather than the other way ’round.
Why you shouldn’t go too large
Aside from the cost and the simple fact that some homes and apartments just can’t accommodate huge tanks, there are three main reasons to avoid buying an XXL (> 100 gallons) aquarium.
Mind the floor
Seriously! Water is heavy, and so are glass, rocks, and gravel. Depending on the structure of your house or apartment, a big aquarium can turn out to be a big mistake. Check whether the floor you’re intending to place the tank on can hold the weight, especially in apartment buildings or if you want to keep your fish upstairs.
Consider: a 150-gallon aquarium with wood cabinet, a normal layer of substrate, and some rockwork can weigh almost a metric ton! That’s a lot of weight sitting in a relatively small area. Some floors simply won’t be able to handle it; if you’re unsure, it’s best to ask a contractor first.
Electricity
Big aquariums come with big heaters, big lights, big filters, and possibly other equipment like a chiller, protein skimmer, wave maker, air pump, and more. Although the LED lights used nowadays instead of classic fluorescents certainly help keep the electricity bill down, heaters in particular can still be quite costly to run.
Consider: a 150-gallon aquarium heated to 76 °F, lit with medium-strength LED bars, can run you $200-450 a year just in electricity depending on where you live. This number goes up if the room the tank is in tends to be chilly, and especially if it’s hot and you need to run a chiller.
Did you know? Speaking of chillers: they’re seriously expensive. Smaller and medium-sized aquariums can be cooled down at least a few degrees using cheap fans, but when you go seriously big, that’s unfortunately no longer an option.
Maintenance
XXL aquariums usually need water changes and cleaning a little less frequently than smaller ones. Better stability tends to mean less algae and may also reduce the need for water changes (though not by a lot). The downside is that when the time does come for aquarium maintenance, each task is bigger.
A 20% water change in a 30-gallon aquarium is about one bucket’s worth; for a 150-gallon, you better have a direct connection to the tap or you’re going to be lugging buckets all day! Likewise, scrubbing algae in a 30-gallon already makes our arms ache, but in a 150-gallon set-up it’s a full work-out.
So, how big should my aquarium be?
Now, everyone has their preferences, but in our opinion—and we have plenty of experience to back this one up, mind you—the ideal freshwater starter aquarium is a rectangular 30-gallon tank. Tanks of this shape are often called “breeders” or just “long”. If a 30 gal is too big for you or the space you’re eyeing, try to at least avoid going smaller than 15 gallons.
For saltwater, which tends to be more finicky than fresh, our recommendation would be to start with a rectangular 55-gallon (long/breeder). We admit this can look dauntingly big if you’re seeing one for the first time, but you’re unlikely to regret it! We promise it’ll appear to magically shrink over time.
If you really can’t fit a 55 into your home, you may find a 40-gallon can also do the trick for a nice reef set-up—but really, those extra 15 gallons do make a difference.
Mind the shape
There’s a reason we specifically recommend a tank that’s longer than it’s wide: it maximizes space. Most fish swim back and forth, not up and down—meaning footprint counts much more than height when it comes to the species you can keep.
We love a good cube, but it does limit your options! When we say a fish needs at least a 20-gallon aquarium, we mean a 20-gallon long, not a tall tank.
Not unimportant: for most folks, long tanks also prove easier to clean simply because they’re shallower. A cylindrical set-up is fantastic to look at—until you realize it’s deeper than your arm is long and you have to use a grabbing tool for maintenance tasks.
Mind the fish
If you already have one or multiple fish in mind that you’d like to keep, this will obviously affect your choice in terms of tank size. If you want to keep freshwater angelfish, don’t grab a 20 gallon no matter how many times the pet store says it’ll work fine—it won’t. As angelfish care guides will reveal, they need 80+ gallons for an appropriate group size.
Thinking about which fish you’re interested in, and basing the size of the aquarium you buy on their needs, is a great way to give yourself some direction in the search for a perfectly-sized tank.
Conclusion
As with most things in life, when it comes to aquarium size, your best bet is finding a middle ground. We recommend a 30-gallon aquarium to start with if you want a freshwater fish tank, while beginning reefers are best off opting for a 55-gallon—in our (professional) opinion, anyway.
Want an aquarium for your home or office, but feel daunted by considerations like tank size? We can help. Contact FantaSEA Aquariums with your ideas and we’ll design, set up, and even maintain your dream tank for you. All you have to do is enjoy it!
