Live Rock (Part 2): How to Safely Add Rock To Your Reef Tank

For Beginners - Live Rock (Part 2): How to Safely Add Rock To Your Reef Tank

When adding live rock to your reef tank – whether you are just starting or have been in the hobby for years – there are a few things to keep in mind that will make it a lot safer.

How Much Rock Should You Add?

The general rule of thumb is one to two pounds of rock per gallon of aquarium water. However, this number depends on the aquascaping.

Before purchasing, create an aquascaping plan and determine what type, shape and sizes of rock you will need. The aquascaping design should give you a rough idea of how much rock you will need. You should always include base rock which is denser and heavier than other types. It’s excellent for creating a solid foundation. Base rock is also very porous, which is particularly helpful for the growth of beneficial bacteria.

Returning live or dry rock can be difficult, so you’ll want to resist the temptation to over-buy. Buy what you need. You can always add more later if needed.

How To Remove Hitchhikers

Mantis Shrimp
Mantis Shrimp

You will want to ensure that you purchase live rock from a reliable source. This will reduce the risk of unwanted hitchhikers. If you don’t want to deal with hitchhikers, buy hitchhiker-free dry rock.

Most live rock hitchhikers – like brittle stars, urchins, and feather dusters – are reef-safe and excellent additions to an aquarium. Before removing any hitchhikers, carefully examine the rock and figure out what you have. If there are harmful hitchhikers – like mantis shrimp, gorilla crabs, aiptasia, or fireworms – you will want to remove them before adding the rock to the tank. This is because it’s much harder to remove them from an established tank. Below are a few different ways to remove them…

Physical Removal

Physically removing hitchhikers is difficult because it’s hard to see into all the little nooks, crannies, and crevices of the rock.

Hypersalinity Dip (Recommended Option)

Place the rock in a bucket of saltwater with a specific gravity of 1.035 to 1.040 for 1-2 minutes. At this salinity level, hitchhikers will exit the rock, making them easy to remove. Add any good hitchhikers that have also left the rock back to the tank. While the process causes stress to the living organism on the rock, it should not induce significant die-off of invertebrates, bacteria or other living organisms.

Freshwater Dip

For most live rock, a hypersalinity dip is sufficient. However, for live rock infested with lots of unwanted pests, a freshwater dip is also an option. A freshwater dip generally lasts 2-5 minutes long. Only use a freshwater dip in extreme cases as good hitchhikers and bacteria will die-off in the process. During the dip, blast the rock with a baster or powerhead to remove dead organisms.



Physically removing aiptasia is not recommended as it can cause aitptasia spores to spread throughout the tank, causing the aiptasia to proliferate as a result.

Additionally, a hypersalinity or freshwater dip generally will not kill aiptasia. The best option for removal is an aipastia specific treatment like F-Aiptasia from Frank’s Tanks, for example.

Do You Need to Cure Your Rock?

Curing will depend on the type and quality of the rock…

Dry Rock

One of the advantages of dry rock is that you generally do not need to do a full curing cycle. In most cases, it is safe to add dry rock straight to a new or existing tank. Just give it a good rinse, then add it to the tank. After adding dry rock, most tanks will need to go through a short mini-cycle as the bacteria colonies populate the new rock. This mini-cycle may cause a diatom algae bloom. Adding live bacteria along with the new rock will generally reduce any negative impacts of this mini-cycle.

Live Rock

Generally, you do need to cure live rock. Due to long shipping times, improper storage, or the type of rock, most live rock will need to be cured before adding it to the tank. If it smells foul, it very likely needs to be cured.

If you don’t know whether or not to cure the rock, add it to a bucket of saltwater with the correct temperature and flow, then test it for ammonia within 24 hours. If the ammonia level is above zero, cure the rock.

How to Cure Live Rock

In a new tank, it is acceptable to cure the live rock directly in the tank. In an established tank, fully cure the rock outside the tank in a large container before adding it to the tank.

  • Step 1 – Prepare Water: Prepare saltwater using RO-DI water and a quality salt mix to a salinity of -1.024 – 1.028 sg and a temperature of 75-78.
  • Step 2 – Add Flow: The more flow, the faster the curing process.
  • Step 3 – Inspect & Clean Rock: Inspect the rock for dead or decaying organic matter and sponges. Remove any dead or unwanted material using a medium bristled brush.
  • Step 4 – Add Rock: Maximize water flow by spreading the rock out throughout the entire tank or container.
  • Step 5 – Test for Ammonia: Test ammonia daily. If ammonia levels climb above 5 ppm, do a 100% water change. Continue testing until ammonia levels drop to 0 ppm.
  • Step 6 – Test for Nitrite: After ammonia reaches zero, start daily testing of nitrite. Nitrite levels will generally spike quickly and then rapidly fall. This process is typically much faster than the rise and fall of ammonia. Nitrite should also be zero before adding the rock to the aquarium.

While curing rock is not a fast process, it is a vital one. The curing process can take anywhere from a week to a couple of months, depending on the quality of the live rock, the shipping time, the type of rock and other variables. Running a protein skimmer and mechanical filter will speed up the process.

When adding live rock to an existing tank, the curing process is even more critical. Adding any rock with hitchhikers can infest the entire tank. Any dead organic material on the rock can cause ammonia, nitrite and other essential parameters to spike.

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