How Big Does A Saltwater Aquarium Really Need To Be?

One of the most common questions asked by a total beginner to saltwater aquariums and a very valid question at that. There are so many tank sizes out there knowing where to start can send you dizzy.

Do not worry you are not alone as we all have been in this dilemma at the start of our journey. The key to your own success is to pick the size that best suits you, your lifestyle and your budget.

A 20 gallon tank is the smallest recommended size for a saltwater aquarium, but a 55-75 gallon tank is perfect for beginners as they allow for greater water stability, fewer parameter fluctuations, lots of room for fish and coral, and not too expensive to initially stock and maintain.

Although there are so many choices there are many things you need to answer to help select the best size to suit you.
Read on to get some of those answers…

How Does Aquarium Location Dictate Tank Size?

Where to physically locate your aquarium is pretty much the first step. The area where your aquarium is going to sit will dictate the maximum size the tank can be.
Are you looking to install it in a cubby, a lobby, a corner of your office or living room, a kitchen counter, your child’s bedroom?

Not only does size matter but also the weight. A small 20 gallon aquarium can easily sit on a sturdy kitchen counter, but a 180 gallon display tank with 50 gallon sump is going to weigh over 2000lbs! Is the floor in your 100 year-old home able to support that weight?

The other decision is that if you have lots of space, I can tell you now that within 2 years you will be wanting a bigger aquarium! It happens to every reefer – It’s like our disease.

Bigger Is Better! – Wiki Source

Because of this, it is always better to buy the bigger aquarium now and spend money once, rather than upgrade everything in 1-2 years’ time, thus spending twice as much in the long-term.

How Does Aquarium Budget Dictate Tank Size?

If this is your first saltwater aquarium budget is most likely going to be the biggest factor in your decision making. Saltwater aquariums are not cheap and the thought of spending a lot of money for it not to succeed is nerve-wracking.

This is where spending as much as you can will ALWAYS improve your chances of success.

The Smaller The Aquarium, The Less Stable It Will Be

Smaller aquariums require less budget. The aquariums are less, the equipment is less, the stocking costs are less but the maintenance time is about the same as a larger aquarium and the biggest factor is stability. Smaller is not always the best policy.

As a beginner, you will make mistakes. A small mistake in a 20 gallon aquarium could affect the water significantly. The same mistake made on a 60 or 75 gallon aquarium may not even be noticed.

Always Buy The Biggest Aquarium You Can Fit & Afford!

Maintaining water parameter stability is what we do as aquarists. We don’t keep livestock, we keep water.

The larger aquarium you have, the more water there is to dilute an error you make. Larger aquariums are less susceptible to room temperature swings and the greater variety in livestock you can have.

I always advise beginners to make their budget for not only the initial setup cost but then how much they can afford to spend each month.

Here are some monthly expenses you will have to account for:

  • Fish
  • Coral
  • Salt Mix
  • Filter Media
  • Food

Granted, most of these will be purchased sporadically like food and buckets of salt mix, but a monthly budget is required because once your aquarium is up and running you are committed.

For a general idea of how much various aquariums cost to run see the article in the ‘Further Reading’ section below.

Click Here to get your Free Maintenance Checklist and Set up Equipment Checklists

How Does Fish Stocking Dictate Tank Size?

It goes without saying that the smaller the aquarium, the less livestock you can have in it. Those mason jars mentioned at the start will only have a few corals in them and maybe one or two sexy shrimp but they require daily attention!

Sexy Shrimp – Flickr Source

Most of the common fish that beginners desire require an aquarium of at least 10 gallons or more. Selecting your livestock that you wish to have will also dictate the size of aquarium you have.

If you are wanting the cast of Finding Nemo you are looking at an aquarium of +150 gallons, but if you wish to have a nice slice of the world’s reef you can begin with an awesome All-In-One bundle like the Innovative Marine 14 Gallon Penninsular.

Nuvo Fusion 14
IM 14G Penninsular Bundle

Creating a stocking list for both fish and coral is a very important task and it is one I recommend you begin before even buying your aquarium. By researching and figuring out what you want and what you can keep in your preferred aquarium size will give you a starting point.

Fish Stocking Examples:

Example #1

2 Oscillaris Clown Fish
1 Cleaner Shrimp
1 Clown Goby
2 Hermit Crabs
4 Snails

Pulsing Xenia

This would be about your limit for the 14G Penninsular

Example #2

2 Oscillaris Clown Fish
1 Clown Goby
2 Bangaii Cardinalfish
Yellow Watchman Goby
Sixline Wrasse
5 Green Chromis
1 Yellow Tang
2 Azure Damselfish
1 Cleaner Shrimp
1 Fire Shrimp
10 Hermit Crabs
20 Snails

Pulsing Xenia
Leather Coral
Candy Canes
Frogspawn Coral
Hammer Coral
Montipora Coral

This would be about your limit for a 60-75G Reef-Ready Aquarium

By researching each inhabitant you wish to have you can see what kind of area it likes to live in the tank, the habitat it likes to feels safe in, what it can be kept with and how much room it needs.

The more diverse the aquarium you wish to own, the bigger the aquarium will have to be.

How To Use Expertise To Dictate Aquarium Size?

Like everything in life. Do not try and run before you can walk. This is true for saltwater. This does not mean you have to start with a small aquarium, but what it does mean is that it is not a race.

By starting with a 45 gallon All-In-One aquarium like the Redsea Max E series aquarium you can have a nice size tank, all of the equipment included and the aquarium and stand look like a piece of art.

Red Sea Max E Series All-In-One Aquariums

The price tag may seem expensive, but when you total up everything you would be needing to buy anyway, you will not be that far off that price.

The key is buying an aquarium that is going to be easy to maintain, not too expensive to stock and has the lighting and filtration you need to keep any fish and coral you wish will give you the best chance of success. No matter which setup you chose, buying one that suits you is paramount.

Aquarium Size Examples

Here I’m going to list some examples of how to select an aquarium:

My Own Setup

My Reef Aquarium
My Reef Aquarium

Location – I had a 4ft space next to the doorway into my living room. Below that space, I had a full-height basement with room to build a ‘Remote ‘Filtration’ area.
My house is 100 years-old but it was easy to brace the floor under my aquarium – just in case.

Aquarium Joist Bracing
My Joist Bracing Installed

Budget – I had $2000 to spend on equipment, installation, and stocking with $100/month ongoing budget.

Stocking – No matter what, I had to have a Yellow Tang and SPS coral. That was as simple a goal as I had. To do this I knew I needed a tank size of at least 75 gallons, good filtration, lighting, and flow.

All the other livestock was added over the first year after diligent research into them, their habitat and requirements.

Expertise – I had extensive expertise but this would be my first dive into keeping SPS. I knew water stability was key so I took my time, bought the best equipment I could, slowly stocked and built my way up to SPS.

Touch wood, I have never had any major illnesses, algae outbreaks or problems.

Solution – Looking at the requirements above I installed a 4ft 75 gallon aquarium with a DIY 20G Long sump, a DIY LED and T5 lighting array with an open aquascape to allow for swimming and SPS growth. The aquarium is thriving.

You can learn more about my installation Here

Childs Bedroom

Location – On the child’s dresser next to their bed. It cannot be heavy or noisy. Preferably a closed lid to prevent wandering fingers or toys.

Budget – $500 to setup. Monthly costs should be small for a small aquarium.

Stocking – Open to options, maybe a pair of Clownfish or a Pistol Shrimp/Yellow Watchman Goby pair. A couple of hermit crabs and some easy-to-keep corals.

Expertise – Complete beginner. No freshwater experience. House has a dog that is walked lots and well cared for.

Solution – Fluval Sea Evo XII All-In-One Aquarium. A great 13.5 gallon starter kit that will be easy to set up and maintain with enough volume to create a nice little piece of the ocean.

Fluval Sea Evo XII Large
Fluval Sea Evo XII AIO Aquarium

A perfect way to introduce your children to responsibility, nature, symbiotic relationships, commitment, budgeting, research, and chores.

For a Complete Guide on setting up this aquarium Click Here

Modern, Minimalist Condo

Location – A central wall in the center of the open-plan living space between the living room to the dining area. The condo is modern with dark granite kitchen countertops and fireplace surround and has the minimalist aesthetic look to the entire home.

The aquarium must be stylish, look pristine and become the focal point of the entire condo.

Budget – $3000 for initial setup with $1000 for livestock and coral over the first year. $50/month for ongoing maintenance consumables.

Stocking – A nice mix of color and fish locating all areas of the aquarium. Corals to add color, texture, and movement. Softies and LPS for ease of care.

Must have a shoal of Green Chromis and a pair of Black & White Clownfish.

Expertise – The last aquarium was a successful Cichlid aquarium with breeding and regular births. Aquarium maintenance, not a problem. First step into saltwater.

Solution – JBJ Rimless 65G AIO Starter Bundle coupled with a pair of AI Prime 16HD LED lights will ensure the LPS not only thrive but show vivid coloration. A stylish, sleek All-In-One aquarium with a good volume to create a nice diverse reef.

Perfect dimensions to allow for a good amount of Live Rock with a pleasing aquascape all while leaving plenty of room for the shoaling Green Chromis.

Filtration is easily accessible with extra room in the stand for an automatic top-off system and chiller if required. Ample room to store all maintenance equipment out of sight.

For a Complete Guide on setting up this aquarium Click Here

To Finish

Setting up your first saltwater aquarium is an exciting time and doing it correctly the first time will not only save you money but will allow you to enjoy watching your piece of the ocean grow.

I always advise you to buy the biggest you can afford and fit and only buy it once. Research as much as you can on every aspect and buy the best-reviewed products.

There is a lot of stuff out there for cheap, which may seem like a bargain at first, but if it breaks after a year or does not keep the coral you want its just wasted money.

I have created a complete series on setting up 10 different sized aquariums ranging from 13.5 gallons up to 140 gallons. Each one comes with a complete list of recommended products sized for that particular aquarium.

In addition, you can find recommended tips, products, and information on everything you need to cycle, maintain & medicate your new bowl of water by clicking HERE

Further Reading

Should you required further in-depth information to some of the topics mentioned here I recommended the following:


Hi, I'm Richard and I have been an avid aquarist for over 30 years with a passion for Saltwater Aquariums. I love to pass on my knowledge to help others get the same amount a pleasure out of this hobby as I do. View my About Me page to find out more about me & my mixed reef aquarium.

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