Determining what size tank is one of the first decisions you will face after making the decision to keep a saltwater aquarium. While there is some debate to be had over the most ideal size, the reef tank community has settled on a few general sizes that are best for beginners.


Ryan's office tank


Best is a tricky word because it is subjective and in this case, best is a balance of cost vs. success rates. The facts are larger tanks often have higher success rates but are more expensive on a variety of fronts. There are two big reasons people tend to succeed more often with larger tanks.


Dosing additives into a reef tank


Larger is better reason #1

The mistakes a new reefer makes are often inevitable and sometimes even predictable. The effects of overdosing, overfeeding, equipment failure or some accidental contaminants become progressively less severe as your water volume gets larger. For example, too much food in a 25 gallon can be the end of it, in a 60-gallon tank a small water change will solve it, and in a 120-gallon tank the impact is minimal.


The reason is changes to the water happen much slower in larger bodies of water. As mentioned before, larger tanks are more costly but the amount of time spent on maintenance between a 60, 120 and 180-gallon tank is not dramatically different.


120 Gallon Reef Tank


Larger is better reason #2

The other reason we see higher success rates and in many cases actually cheaper is the upgrade factor. Successful smaller tanks in the 6-24 months range probably have and upgrade factor somewhere around 3 to 1. Meaning if you experience success on a smaller tank you are very likely to invest in something larger and upgrade.


With larger tanks say more than 75 gallons, reefers tend to be happy with these sizes for 5 years or more and the tank will often end up being their forever tank. Therefore, the upgrade factor is pretty low in these cases so your overall costs can be as much as half. One large tank upfront is going to be far less expensive in the long term compared to a small tank first, then a larger upgrade 24 months later.


BRS360 Framed in PVC with Dimensions


Get the biggest tank within your means

A larger tank does cost more and not just the tank alone but also much of the equipment is larger and more costly. You can pretty much expect to double the amount of coral and fish in a tank that is double the size as well, again adding to your overall expense.


This is a rare case because it is probably universally agreed upon by the reefing community at large, when building your first tank get something as big as your budget and space allows. The maintenance between the common new tank sizes is nominal, the biggest difference is just increased cost and increased chances of SUCCESS!


Best tank sizes for beginners


What are the best beginner tank sizes?

There are 5 tank sizes that immediately add to your success and one of them will surely speak to you. A 40-gallon breeder, 60 cube, 93 square, 120 or 180-gallon rectangle.


The 40 breeder is probably the most popular first reef tank for a few solid reasons. First off, the tank is really affordable in most cases. Time it right and catch Petco during their one dollar per gallon aquarium sale and your new tank will only cost you $40 bucks.


40 breeder standard black framed aquarium


The shape is perfect too where it is nearly as deep front to back as it is tall which means it supports the type of rockwork or “aquascapes” that are ideal for coral growth and what most reefers will prefer. Really tall tanks, cylinders, corner tanks or just odd shapes in general will prove to be difficult for a number of reasons.


Finally, the 40-gallon size is about the minimum tank size that will support juvenile versions of utilitarian fish that are critical to a new reefer’s success and exactly why we recommend nothing less than 40 gallons for your first saltwater aquarium.


Combine all of this with that dilution factor we talked about earlier where larger is often easier and you can clearly understand why success rates are much higher with tanks 40 gallons or larger.


Cube shaped reef tank


In terms of the 60 cube and 93 square, both are very cool tanks to have when wall space is limited because you still get that equilateral depth and height which simply makes it easier to aquascape with live rock and gives you plenty of space for coral growth. You will likely also find that keeping the tank clean, dialing in water flow and providing sufficient light is also easier with these cube tanks.


In fact, when it comes to lighting a 24” cube tank (60 gallon), it will only require a single light whereas the 40 breeder will likely require two of those same lights for effective coverage. That means the total setup costs could end up being about the same and you get 20 extra gallons of water.


After these cube tanks, the dimensions just get wider so be sure to consider your wall space.

  • 40 breeder - 36” x 18” x 16”
  • 60 Cube - 24” x 24” x 24”
  • 93 Cube - 30” x 30” x 24”
  • 120 Gallon - 48” x 24” x 24”
  • 180 Gallon - 72” x 24” x 24”

Aquariums and Stands product page


Here are the facts

The 40 breeder is the number one most popular beginner tank because of the affordability and a manageable size. The 60 cube and 93 square are perfect when space is a concern.

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The 120 and 180-gallon are less common starting sizes but they are the two most common upgrade sizes meaning after you have had a taste of success, these are the two most common tank sizes you will upgrade to. If you have dreamed of reefing for a long time, you know that aquariums are in your DNA and want to avoid the costly upgrade path, start with a 120 or 180-gallon tank.


What's Next

After deciding what size you want, the next step is learning about the different options you have in terms of filtration - Sump, AIO or Glass Box?.


5 Minute Saltwater Aquarium Guide


Looking for a different topic or have questions? You can binge the entire 5 Minute Saltwater Aquarium Guide playlist right here on our website. We also invite you to join the #askBRStv Facebook Group which is a free resource for you to ask questions, get advice, interact with other hobbyists and get your daily reef aquarium fix.