Fish are popular pets. In fact, they’re right up there with dogs and cats in popularity. Unlike our four-legged friends, though, fish are a little less complicated to care for. Granted, they also aren’t as affectionate as canines or as cute as felines. But no one can deny that staring at a nice, well-maintained and appropriately lighted fish tank can be very, very relaxing.

A few years back, I desperately wanted a pet. I lived by myself and the apartment just felt too lonely sometimes. Unfortunately, there are two things barring me from getting a puppy. One, I am allergic to dogs. And two, the apartment complex I lived in doesn’t allow it anyway.

So what’s a gal to do? I started looking at aquarium for sale ads, that’s what. I figure I can easily tell my landlord having a fish tank doesn’t necessarily mean I have a pet. It’s more of a décor. (I realized later on that the no pet clause didn’t cover aquaria anyway so I didn’t really have to make up excuses, yay!)

First on my agenda was looking for an actual fish tank to fit my place. I was told popular fish tank sizes are the 29 gallon aquariums and the 75 gallon aquariums. Of course, I thought that both sounded huge for a novice like me. I wanted maybe something smaller. (I did eventually get those sizes when I upgraded, though. I wrote some reviews here.)

Anyway, I didn’t know then that there were so many aquarium sizes available. Here’s a guide to aquarium sizes in the US, courtesy of Wikipedia:


Volume Length Width Height
9.5 Litres (2.5 US G.) 30.5cm (12″) 15.2cm (6″) 20.3cm (8″)
18.9 Litres (5 US G.) 40.6cm (16″) 20.3cm (8″) 25.4cm (10″)
37.9 Litres (10 US G.) Long 50.8cm (20″) 25.4cm (10″) 30.5cm (12″)
56.8 Litres (15 US G.) 61cm (24″) 30.5cm (12″) 30.5cm (12″)
68.1 Litres (18 US G.) Tall 50.8cm (20″) 25.4cm (10″) 45.7cm (18″)


Volume Length Width Height
75.7 Litres (20 US G.) Tall 61cm (24″) 30.5cm (12″) 40.6cm (16″)
75.7 Litres (20 US G.) Long 76.2cm (30″) 30.5cm (12″) 30.5cm (12″)
94.6 Litres (25 US G.) 61cm (24″) 30.5cm (12″) 50.8cm (20″)
109.8 Litres (29 US G.) 76.2cm (30″) 30.5cm (12″) 45.7cm (18″)
113.6 Litres (30 US G.) 91.4cm (36″) 45.7cm (18″) 30.5cm (12″)
151.4 Litres (40 US G.) 91.4cm (36″) 45.7cm (18″) 40.6cm (16″)
151.4 Litres (40 US G.) 121.9cm (48″) 30.5cm (12″) 40.6cm (16″)

Large size

Volume Length Width Height
189.3 Litres (50 US G.) 91.4cm (36″) 45.7cm (18″) 48.3cm (19″)
208.2 Litres (55 US G.) 121.9cm (48″) 33cm (13″) 53.3cm (21″)
246.1 Litres (65 US G.) 91.4cm (36″) 45.7cm (18″) 61cm (24″)
283.9 Litres (75 US G.) 121.9cm (48″) 45.7cm (18″) 53.3cm (21″)
340.7 Litres (90 US G.) 121.9cm (48″) 45.7cm (18″) 61cm (24″)
473.2 Litres (125 US G.) 182.9cm (72″) 45.7cm (18″) 53.3cm (21″)
567.8 Litres (150 US G.) 182.9cm (72″) 45.7cm (18″) 71.1cm (28″)
681.4 Litres (180 US G.) 182.9cm (72″) 61cm (24″) 63.5cm (25″)

If you think picking a size off the US chart is daunting, then you should know that UK-made aquariums actually have a different sizing guide:

Small UK

Volume Length Width Height
12 Litres (3.2 US G.) 30.5cm (12″) 20.3cm (8″) 20.3cm (8″)
14 Litres (3.7 US G.) 35.6cm (14″) 20.3cm (8″) 20.3cm (8″)
16 Litres (4.2 US G.) 40.6cm (16″) 20.3cm (8″) 20.3cm (8″)
24 Litres (6.3 US G.) 61cm (24″) 20.3cm (8″) 20.3cm (8″)
18 Litres (4.8 US G.) 40.6cm (16″) 25.4cm (10″) 20.3cm (8″)
28 Litres (7.4 US G.) 45.7cm (18″) 25.4cm (10″) 25.4cm (10″)
40 Litres (10.6 US G.) 45.7cm (18″) 38.1cm (15″) 25.4cm (10″)

Medium-sized UK

Volume Length Width Height
70 Litres (18.5 US G.) 61cm (24″) 38.1cm (15″) 30.5cm (12″)
89 Litres (23.5 US G.) 76.2cm (30″) 38.1cm (15″) 30.5cm (12″)
127 Litres (33.5 US G.) 91.4cm (36″) 45.7cm (18″) 30.5cm (12″)
168 Litres (44.4 US G.) 96.5cm (38″) 45.7cm (18″) 38.1cm (15″)
142 Litres (37.5 US G.) 121.9cm (48″) 38.1cm (15″) 30.5cm (12″)

Large UK

Volume Length Width Height
170 Litres (44.9 US G.) 121.9cm (48″) 45.7cm (18″) 30.5cm (12″)
212 Litres (56 US G.) 121.9cm (48″) 45.7cm (18″) 38.1cm (15″)
212 Litres (56 US G.) 182.9cm (72″) 38.1cm (15″) 30.5cm (12″)
255 Litres (67.4 US G.) 121.9cm (48″) 45.7cm (18″) 45.7cm (18″)
340 Litres (89.8 US G.) 121.9cm (48″) 61cm (24″) 45.7cm (18″)
425 Litres (112.3 US G.) 152.4cm (60″) 61cm (24″) 45.7cm (18″)
453 Litres (119.7 US G.) 121.9cm (48″) 61cm (24″) 61cm (24″)
510 Litres (134.7 US G.) 182.9cm (72″) 61cm (24″) 45.7cm (18″)
566 Litres (149.5 US G.) 152.4cm (60″) 61cm (24″) 61cm (24″)
680 Litres (179.6 US G.) 182.9cm (72″) 61cm (24″) 61cm (24″)


Simply put, the UK sizes are smaller than their US counterparts. But really, the question is what size should you choose? What works best for you?

Here are a few guidelines to help you out while you make up your mind.

The kind of fish you want will affect your aquarium size choice.

  1. Decide on what kind of fish you want to keep as that will affect how big an aquarium you must have.
  2. Small schooling fish are generally okay in a 10 to 30 gallon aquarium. Bear in mind, of course, that lower capacity means less fish.
  3. Always look at the maximum size of the fish species. You need to prepare and get a bigger aquarium if you chose fish that grow to larger sizes. In this case, the minimum you need to get is at least 40 gallons.

The number of people in your household can also impact your choices.

  1. A family of fish hobbyists may do well with a 29-gallon aquarium. It’s big enough to hold a good number of fish but small enough so maintenance isn’t so hard.
  2. A more experienced family can opt for a 55-gallon aquarium. That’s big enough to allow for fish schools and larger species like eels and catfish. It’s also spacious enough to keep the aquarium inhabitants in peaceful co-existence.
  3. The most popular large aquarium size is the 90 gallon tank. But that’s going to weigh a thousand pounds filled with water so placement may be a problem.

Personally, I decided to stick with some fancy goldfish for my first aquarium. They’re pretty to look at and don’t look like they’d need much from me. I did get a 30-gallon aquarium because I was told they can grow a bit and I didn’t want to have stunted goldfish.

What I ended up getting was something like this 30-gallon All Glass aquarium.

That one’s around $318 from Amazon and weighs over 40 pounds. The actual dimensions are 36.2 x 12.6 x 16.8 inches. I got mine second-hand from a friend of a friend but it’s pretty much the same thing. It’s a very straightforward piece. Just a standard rectangle tank made of sturdy glass. The one pictured is manufactured by All Glass and comes with black or oak trim. Mine had a faded black trim but that may be because it’s not brand new. It did its job so no complaints from me.

I did look at a 55 gallon aquarium but was a bit too much for a beginner, I thought. The Marine Aquarium Kit from Carolina looked quite awesome. It’s pricey but it comes with everything but the fish. I saw this when I was looking for my first aquarium and frankly, was a bit overwhelmed. Look at it, it’s huge!

The whole thing will set you back over $750 before the fish, décor and other essentials like filters and such. The price includes the fish tank, the stand and supplies.

And then there was this 90-gallon aquarium I was lusting after but I think I might have to live inside it too if I put it inside my tiny apartment.

I did end up buying that, though, years later and after I moved to a bigger house with the significant other and the kids. Actually, if you must know, it’s still sitting in our basement housing an assortment of aquaria. It wasn’t cheap at about $700 but it was well worth the money.

It’s manufactured by Deep Blue Professional and came with an overflow system that worked really well with the filtration system we installed. The result was a quiet and efficient tank with good circulation and filtration. Not bad for the small fortune we spent setting everything up.

By the way, contrary to popular belief, aquariums don’t always have to be rectangular in shape. There are many different shapes available. There are hexagonal, bow front and 5-sided tanks. I actually reviewed a few unique tanks before. There’s also the option to have a tank customized but you may have some trouble fitting standard lighting fixtures on them.

Oh and if you have really limited space and just want a nice, small fish bowl, I would advice thinking twice. Fish bowls are cute. But they also don’t have a lot of space and aeration can be a problem. And that limitation in gas exchange means your aquarium water could become smelly. It could also result to the premature death of your beloved pet. Remember, in general, the larger the aquarium space, the more sustainable a habitat it is.

Finally, be smart about buying an aquarium and maybe just look for a packaged starter kit within your budget range that already has everything. I failed to do that and ended up spending so much more than I could have.

That’s it. Good luck with the fishies!