Aquarium Fish

Live Rock for Saltwater Aquariums

What is Live Rock?

Live Rock is rubble that has broken off a coral reef structure by natural means such as hurricanes and tropical storms. This broken off rubble is called live rock because of all the living organisms that are found on and within the rock. Many types of algae, crabs, marine worms, small crustaceans, bacteria and other life forms make their homes on the reef structures found in the ocean and when you buy saltwater live rock you'll most likely be getting some of these organisms.

There are numerous benefits from using live rock in your marine aquarium and we'll explore some of these benefits now.

Aside from an abundance of saltwater aquarium keeping information, saltwater live rock could be considered one of the primary reasons so many people are successfully keeping saltwater tanks these days.

Live rock is usually extremely porous and is used as the primary biological filter in saltwater tanks that have it. The many holes and crannies in this rock give it a tremendous amount of surface area for the beneficial aerobic (needs oxygen) and anaerobic (does not need oxygen) bacteria to live on. This is what makes saltwater live rock such a great biological filter for your tank. The beneficial bacteria helps convert the ammonia from fish waste and uneaten fish food into nitrIte. The second step is when this bacteria converts the nitrIte into nitrAte. The last step is when the anaerobic bacteria converts the nitrAte into harmless nitrogen gas that escapes via the water surface. If you're curious to find out more information on this cycle, please read the aquarium nitrogen cycle page.

New rock, curing in the tank
Saltwater Live Rock
Same rock, 3 months later
Saltwater Live rock after 3 months in tank

How well saltwater live rock can completely cycle the aquarium has a lot to do with how much rock you have in your aquarium. Many hobbyists try to get at least 1 pound per gallon for fish only tanks (FOWLR) and 2 pounds or more per gallon for a marine reef tank setup. You'll definitely need to monitor and test your water quality periodically to check for nitrAtes. If your readings are out of the acceptable range for your tank inhabitants you will need to perform water changes to bring the nitrAte levels within acceptable range.

As your fish grow they will produce more wastes and they may end up producing too much for your rock to adequately filter. Using a protein skimmer is still recommended with live rock tanks.

Saltwater Live Rock Benefits

Some of the benefits that you can expect from using live rock:

  • Saltwater live rock is a fantastic biological filter

  • Provides many hiding and living spaces for your saltwater fish and invertebrates

  • Can be a source of food for your saltwater fish and invertebrates

  • Purple and pink Coralline algae that will grow on the rock can be extremely attractive.

    Purple Coralline Algae Encrusted Live Rock Purple Coralline Closeup of Rock

  • The many organisms that spring to life after your rock has finally cured can be just as fascinating as the fish in your tank. We can't tell you how many hours we have wasted just looking for what's new on our rocks.

  • Rock scaped saltwater aquariums are more natural looking. It's kind of like having a heavily planted freshwater aquarium

  • You can easily attach corals in a reef tank setup to live rock using aquarium safe glue and you can sometimes even insert the plug corals come on into a natural hole or crevice in the rock.

  • You should have a much better experience with keeping saltwater fish if you use live rock because of the biological filter and food source reasons.

3 month old rock
3 month old live rock

While researching saltwater live rock you're going to come across some different types of rock. There are basically two main types of live rock - cured and uncured.

Pre-Cured or Cured Live Rock

Cured live rock is rock that has been in the retailer's tank for a few weeks, at least. The retailer will scrub off any dead or dying organisms from the face of the rock and then cure it by placing it in a high-circulation curing tank. They also sometimes spray a continuous mist of saltwater over the rock that helps to remove the dead organisms. After a few weeks or even a month of this process the rock is considered ready to ship.

Getting cured live rock is going to cost much more than getting uncured live rock but it's usually worth the extra expense. Curing live rock in your home can be a very smelly and dirty project.

Even though there can be a significant die off during the curing process, many of the living organisms make it through the pre-curing process at the retailer. You will still need to cure it again once you get it home because some of the organisms will have died during shipment before it reaches your house. It just won't take as long to cure again as uncured live rock. Because of the die off during shipment, you should never place live rock (pre-cured or uncured) into an established tank. Doing so may cause an ammonia spike.

Uncured Live Rock

Uncured live rock is usually a third of the price of cured rock. Hobbyists on an extremely tight budget usually opt for this type of rock. The major drawback is that you're going to see a much greater die off rate then the pre-cured rock and you'll need to get the materials to do the curing process yourself.

If you're setting up a new tank with no other livestock in the tank yet, you can cure the saltwater live rock in the new tank. If not, you can use cheap plastic containers or trash cans as the curing containers. After you scrub off the dead organisms and other debris from the rock, place it in the curing container. An old tooth brush can work fairly well for scrubbing off the dead organisms. Hook up a thermometer, a power head and a protein skimmer to the container. Fill the containers with premixed, aged saltwater and you're ready to go. You will need to monitor the water parameters with your test kit(s) for ammonia, nitrite and nitrate and perform frequent water changes during the curing process. Once you no longer detect ammonia and nitrite and there is no longer a foul smell, you can consider the process complete. How long it takes depends on the shape the rocks in when you start the process.

New rock, fresh from dealer
Live Rock
Same rock, 3 months later
Same live rock after 3 months in tank

Live Rock Types
These are some of the types of live rock you may come across:

  • Base Rock - This is rock that is usually found "under the pile" and it is usually a little cheaper than the other types of rock because it has less living organisms and algae living on the surface. You can save a few dollars by using this as the base to the rock structure in your tank.

  • Pacific Rock - This is rock that comes from Fiji, the Marshall Islands, Indonesia and other locations in the Pacific. It is usually the better choice because it is more porous than the other types of rock. It will also usually have more caves and holes in it. Frequently, this is the most expensive type of rock. It can sometimes be labeled as Pacific Rock or Fiji Premium Rock.

  • Atlantic Rock, Gulf Rock and Caribbean Rock - This is rock that comes from each area as labeled. It is usually not as porous as the other types of rock and might not be the best choice for your tank.

  • Aqua Cultured - This is porous rock that has been placed in the ocean artificially and left for several years so that beneficial bacteria and other organisms can populate the rock. This is the most environment friendly type of live rock you can get.

Where Can I Get Live Rock?
Once you start looking for saltwater live rock you're going to realize that this stuff can cost some serious money. However, think about what it takes to get this material from the ocean. Divers must collect it, retailers have to pre-cure it and then finally deliver it to your door. If you live in the middle of your country be prepared to pay even more in shipping costs. If you're lucky enough to live in a coastal area or you have access to a really good saltwater pet shop that stocks live rock, you can save alot of money in shipping costs by picking it up yourself. Use a search engine and enter "buy live rock" or something similar. If you come across a retailer that you've never heard of you should use the search engine and research them or sign up in a saltwater fish forum (we have one here, the forum links is in the left navigation) and get recommendations from other hobbyists before buying.

The best part about all of this is that Saltwater live rock can be a renewable resource if harvesters practice proper collection techniques. Unfortunately, many do not practice proper collection techniques for the sake of money. This is both short sighted and foolish. Check with buddies or check on forums for recommendations for a good retailer. Try to find out how the rock is being collected before you buy it. You may not get a straight answer, but we need to be diligent in not rewarding those that harm the environment and the coral reefs.

Tips on Growing Coralline Algae

  • Keep your water parameters in line with regular partial water changes.
  • Get a test kit for alkalinity, magnesium, pH and calcium. If these parameters are dropping too much in between water changes, dose these elements and try to keep the pH in the 8.2 - 8.4 range. Kalkwasser works well to keep alkalinity and calcium levels up but be extremely careful dosing with kalkwasser (slow drips), especially in smaller tanks! Kalkwasser is extremely basic and can cause extreme swings in pH. Regular partial water changes should work great for most hobbyists without extensive stony coral growth and should help keep the calcium, alkalinity, pH and magnesium levels where they need to be for good coralline growth.

Author : Mike FishLore

Live Rock Video

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