How Much Live Rock Per Gallon Do I Need?

How much live rock per gallon should I use?


how much live rock do i need


There are many questions that normally get asked around the saltwater community. The question of how much live rock per gallon do I need? is probably asked the most.

The answer to that question is that you really only need around 10-20 pounds of live rock to set up a saltwater tank. But there are some variables that I will point out to explain.

I know you probably heard many times that you need 1-2 pounds of live rock per 1 gallon of aquarium size or water volume. That is the common answer that everyone gives to the question but it is simply not accurate. It is a great rule of thumb but not a requirement by any means.

In many years of keeping saltwater tanks, I don’t think I have ever had 1-2 pounds of live rock per gallon. Perhaps I did but I wasn’t counting.



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Do you need live rock to start a saltwater tank?


No, you don’t but it is helpful to have if possible. Live rock is used when setting up a saltwater tank as it is the lifeline of your system. Healthy live rock is crucial to a tank’s success. It houses most of the beneficial bacteria your tank needs to thrive.

Most people will use live rock to aid in the start-up cycle of their tank. A new saltwater tank will take around 4-8 weeks to finish it’s cycling before you should add fish.

One thing to keep in mind is the fact that live rock is very expensive to purchase. Most saltwater stores will charge anywhere from $5 to $15 per pound. So 100 lbs of premium live rock could cost you anywhere from $500-$1500!

Live rock is very valuable as it is most desired to have in your tank. It’s very natural-looking and beneficial to have. But you need to be cautious when buying live rock as well, it’s common to accidentally add unwanted hitchhikers to your tank, like aiptasia which could end up being disastrous.

Many hobbyists will choose to start their tank with dry rock only and let the tank cycle without the risk of something bad being introduced or leached into the aquarium. It is much cheaper to start the tank with dry rock as it normally will cost around $2-$5 per pound.

For example, the Natures Ocean dry base rock on Amazon is very cheap and the Caribsea Life Rock is a bit more expensive but still an affordable option.

My personal choice is to use around 10-20 pounds of live rock to setup a new tank, then add dry rock as the remainder.

It’s a good idea to only buy live rock from a trusted source, either from someone you know who has a healthy tank or a fish store either local or online that is known for quality rock.


how much live rock per gallon

Wait! You said you don’t need 1-2 pounds live rock per gallon tank size. Why not?


So here is the deal on that rule of thumb everyone talks about. Have you ever heard the rule of 1-inch of fish per 1-gallon aquarium size? Well, that’s a horrible rule to follow in the aquarium hobby. If you had a 10-gallon aquarium, would you put a 10-inch fish in it? No.

You see that rule will only apply in 2 ways. Either you have to have a very large tank, or only keep tiny fish that don’t grow.

Everything you decide to have in your saltwater aquarium needs to be planned ahead of time. The amount of live rock and livestock included.

If you have a 75-gallon tank, following the rule you should have between 75 and 150 pounds of live rock. Your tank dimensions will play a role as well. if you have a 3-foot long tank, you may not fit as much rock as you would with a standard 4-foot tank.

If you have a custom tank and the dimensions are taller than wider, you may only need 30-50 pounds of live rock to be set up the way you like.

Another option is to have some live rock inside your sump tank. I have seen many saltwater tanks with a small amount of rock in the display and a majority of it sitting in the sump. Personal preference, rock size, and tank dimensions play a role. Another factor being your budget.

Don’t get me wrong here, yes live rock is very valuable and generally, lots of live rock is good for your tank. But there are times when having 1 or 2 pounds per gallon just is not possible or desirable. You can get away with much less and have a very healthy tank.

Here is an example of my 32 Gallon Biocube tank. I only used about 20 pounds of live rock in this setup. My 120-gallon reef tank only has 70 pounds.

There are other ways you can supplement the biological filtration function of live rock as well. There are many different media you can use to house biological bacteria.


how much live rock per gallon

Do you need live rock at all?


Not really. You can get away without having any live rock in your tank but it would be a better choice to have it. As mentioned, it really is important for the majority of beneficial bacteria to populate and grow.

If you don’t like the rock look in your tank, you can decorate other ways and have biological filtration through filters, sumps, and media. But for the most part, live rock is the way to go.

You always have the option of starting out with a small amount of live rock and add to it over time. You don’t need to start a new tank with all the live rock at once. It can be easier on the wallet that way as well.

So overall, the amount of live rock you use is based on personal preference, your budget, tank size. You may end up with 1 pound per gallon but it is not a requirement.

Hope this article was helpful.