Inspiration for beginners: A "before" photo of a new 70G.

Photo courtesy of @Mal1124, ©2018, All Rights Reserved.

Inspiration for beginners: An "after" photo of the same 70G, 21 months later.

Photo courtesy of @Mal1124, ©2018, All Rights Reserved.

When most beginners decide to set up an aquarium, they choose the aquarium first and then figure out what to put inside it. With saltwater, it’s much better to decide first what you hope to have someday in your tank, and then choose the aquarium best suited for the livestock.

In this article, I’m not going to address the glass versus acrylic debate or even where to place your aquarium because those are large topics in and of themselves.

Let's assume for a minute that you haven't purchased your tank yet. Or you're buying your second tank or third. Then this article is for you. The size and shape of your aquarium have plenty of subtle and not-so-subtle effects on both the livestock and the aquarist. So, let’s take a look at some aquarium sizes and shapes and talk about the implications.

A 54-gallon Red Sea Reefer 25o

Photo courtesy of @Chilli ©2018, All Rights Reserved.

Size in general:

You’ve surely heard this before, but it bears repeating: larger saltwater aquariums are more stable than smaller saltwater aquariums, all things being equal (which they rarely are.) For this reason, larger aquariums tend to be easier for beginners to keep the water quality stable than smaller aquariums. And with saltwater aquariums, excellent water quality that stays within a narrow range of parameters is what you’re aiming for.

Of course, size is relative. So, a 10-gallon aquarium will be more stable than a one-gallon, but a 50-gallon will be more stable than a 10-gallon.

Lots of people start with a pretty small aquarium and do fine. It certainly can be done. I just want to emphasize that you have a bit more margin for error with a bigger tank.

A 12-gallon "nano" aquarium.
r2r12g FTS.jpg

Photo courtesy of @Nano sapiens ©2018, All Rights Reserved.

Aquarium size and the aquarist:

As you go up in size, the aquarium is more work, and it’s also more expensive. For example, if you want to change some water in a 20-gallon aquarium, 10 percent of 20 gallons is two gallons. For the sake of discussion, let’s say each gallon of seawater weighs about 8.5 pounds. It’s not that hard to carry two gallons up or down stairs. Not all of us will have the luxury of piping new saltwater directly into the aquarium or old saltwater out to a drain. If you have a very high-tech tank, maybe you can automate this, but for the rest of us mortals, we carry the water.

If you have a 100-gallon aquarium, and you want to change 10 percent of the water, now you have 10 X 8.5 pounds or 85 pounds of water. That’s 85 pounds out and 85 pounds in. I don’t know about you, but I can’t lift that in one go. So, now you have at least two trips up and/or down the stairs or outside or wherever.

I’m not trying to scare anyone away, and plenty of aquarists do this. But for beginners, it’s definitely something to think about. And there are some aquarists who change very little water, and some who change almost no water, especially with mature tanks.

You have to consider the space, too. Do you have room for a big tank? If you’re going to put it on your desk in your office, then obviously you can’t put a massive tank on there. Can your floor support the weight?

The expense is bigger, too, but it’s hard to quantify because there are so many variables. A bigger tank will (probably) need a bigger protein skimmer. More volume of water changes means more salt. The bigger tank needs more powerheads for flow, more heaters and you’ll probably want more livestock, too. You get the idea.

Bigger tanks also tend to have a sump. Some people have sumps with small tanks. Have you thought about where to put your sump? Under the tank? In another room?

A 240-gallon in-wall tank.

Photo courtesy of @Joe Brown ©2018, All Rights Reserved.

The livestock:

If you have a fishless system, and yes, some people do, then I would not be overly preoccupied about the square footage available for snails--they don't move fast. But, fish, on the other hand, can get stressed, and they can get depressed, too. Some readers will go berserk when they read this, but I’m not kidding. This is documented in serious peer-reviewed research. (I did find one study that says, no, fish don’t feel pain, but you could argue that how we measure this may be flawed. The study is cited below with the others.)

In fish, just like in mammals and humans, stress and depression affect health, longevity, and behavior. And one of the things the aquarist can do for the overall health of their fish is give them as much room as possible--within reason--to swim around and not to overstock the tank. Bottom line? The more room you can give your fish, the better.

Furthermore, corals can engage is chemical warfare, anemones can sting other anemones or corals or fish. The list is endless. The more room you can give your livestock, the better. Or else, just don’t overcrowd your tank.

A 40G Breeder used as a room divider.

Photo courtesy of @Codym808. ©2018, All Rights Reserved.

Shape in general:

Tanks come in all shapes and sizes. Tall, short, bowfront, wide, square, round and if you want to spend an unlimited amount of money, you can have custom-built all kinds of weird shapes.

Aside from your fish having enough room to swim around in width or length, there are other things to consider.


Some people like the look of a high tank. I've personally seen some spectacular ones in hotels and restaurants.

Most fish, however, are more inclined to swim side to side than up and down. There is livestock that specifically requires a tall tank: some cephalopod molluscs like the nautilus and some jellyfish come to mind. However, by and large, the tall tanks are for the aquarist’s aesthetic eye and not necessarily for the livestock within.

With a tall tank, you have a few things to consider. First, the surface area per unit volume is smaller than a rectangular or square tank of average height (18’-24”). And the surface is where you get a lot of your gas exchange or how you help oxygenate your tank. Now an appropriately sized protein skimmer can make a big difference with oxygenation, and there are other things you can do to up your oxygen, but surface area is something to think about.

A tall tank is also harder to aquascape. Is your live rock going to be like the Empire State Building? Good luck with that. And the very tall tank is harder to equip and circulate the water.

But maintenance is a big thing here. My arm is 21” from my shoulder to my wrist. If I had a 30”+ tall tank, I’d have to get on a ladder to stick my arm in it. And unless I want to soak my head and wear a snorkel, I’ll never reach the bottom. And those long-arm gloves from the veterinarian only reach the shoulder.

Yes, there are instruments you can buy that are 12”-24” long, forceps and scissors, and other, but my point is, it’s more difficult. More complex. It’s something to consider.

Also, keep in mind that the water pressure at the bottom of the tank is dependent on depth. That means a tall tank has lot more pressure against the walls and corners at the bottom than a less tall tank. Just sayin’. That's why hydroelectric dams are wider at the bottom.

Hydroelectric Dam

Photo is a royalty-free image from Pixabay.

Shorter tanks have the opposite problem. You can fit your arm in there, but were you planning on a deep sand bed for a substrate? A DSB is a minimum of 4” and probably closer to 5”-6”. If your tank is only 18” tall, then now it’s only 12” tall. You’re not going to get Mount Vesuvius in there if that was your plan. Think bungalow instead of the Tower of London for your aquascape.

All-In-One (AIO) tanks

AIO tanks have a lot of the “business” built into the tank: some filtration, maybe an overflow, etc. Consider where the tank will go before getting a tank like this because if you want your tank as a room divider with full view on both sides, then the cords, and other hardware may be unsightly or in the way.

The advantages of AIO tanks are the same as the disadvantages. You don't have to think too hard because most of what you need is already in place. When you learn more, you may want different components that may not be easy to change. But they're often plug-and-play or close to it. And they come in all sizes.

Furnishing your house with aquariums.

Photo courtesy of @saltyhog ©2018, All Rights Reserved.

Round tanks

Some people choose a round tank as an artistic thing. Because it’s unusual. In fact, round tanks are often used in research and breeding because baby fish fry can get stuck in the corners of, well, tanks with corners. And squid are typically kept in round tanks, but they don’t do well in captivity, so we’re not going to spend a lot of time on them here. Hint: I think Acro Al has his clams in round tanks.

A 36-gallon bowfront aquarium as a focal point.

Photo courtesy of @sstanley223 ©2018, All Rights Reserved.

Bowfront tanks

Bowfronts are beautiful. Especially if you want the tank to be the focus of a room. But they are more expensive than flat glass or acrylic, they can be harder to clean, and there is often some distortion of the view depending on the angle you’re looking into the tank. This can make photographing the tank inhabitants a bit more difficult, if you’re into that.

I’m a great believer in live and let live. Get any kind of tank you want; just be aware of the issues that some tanks come with because of their size or shape.

A 120-gallon tank.

Photo courtesy of @dbl ©2018, All Rights Reserved.


Morphologic Effects of the Stress Response in Fish Doccuments/1987/F/1987_F4.pdf

Special thanks:

Special thanks is due today to a lot of individuals who started posting photos of their tanks in a hurry when I asked for it on the forum. I couldn't use every photo posted for this article, but I will use them in the future. Thank you @Efranco @kschweer @Sailingeric @Chilli @MSB123 @DSC reef @Butuz @KLS1993 @saltyhog @noahreefer @Be102 @Lovemyreef2015 @Codym808 @nicodim55 @sstanley223 @cpage101 @MSB123 @Paleozoic_reefer @Joe Brown @Greg Gdowski @khushtram @vetteguy53081 @Mike220 @Nano man @dbl @Mal11224 @Kit_Kat @loudermilkjohn65 @UM Aquarium Club @Deiblerj @Roush427R and I hope I didn't forget anyone. Also, a special thank you to @PDR who is readily available to read article drafts and make suggestions.


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Author Profile: Cynthia White

Cynthia received her BA in English from NYU. She has been a freelance writer and editor for over 20 years. Now she is a writer and editor on staff at R2R, where her forum nickname is Seawitch.

For 15 years, she kept a dozen freshwater tanks, bred cichlids--Cyphotilapia frontosa--and sold them to pet stores in Calgary. Finally, after years of study, she has come to saltwater side. She lives in British Columbia, Canada, with her husband and three special-needs dogs, a five-minute walk from the Georgia Strait, the Pacific Ocean between Vancouver Island and mainland British Columbia, where the water temperature ranges from about eight degrees C (46F) in the winter to 15 degrees C (60F) in the summer. Bring your dry suit. And some hot coffee.
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