Live Rocks: Everything you Need to Know
- Feb 06, 2022
- Anshika Mishra
- 1023 0 0
When reef keeping first began, traditional saltwater aquarists were confused by live rock. How could rock be living? But once they saw a reef aquarium where the stones were bursting with marine life like coral, encrusting algae, and sponges, it was clear that reef rock played a vital role in reef tanks.
At first, we thought rocks were just a structure to place corals and space for shrimps and crabs to explore. But, over the years, aquarists and marine biologists found that most of the life associated with reef rock was microscopic.
The rough surface of live rock and the microscopic pores created by reef-boring algae and fungi are home to an invisible jungle of marine microorganisms that work behind the scenes to maintain a reef ecosystem.
Biofilm and Live Rocks
A recent discovery showed that coralline algae are the preferred landing spots for corals larvae. That's not new. But, what's new is that certain corals prefer specific species of coralline algae. Each species of coralline algae has its unique bacterial biofilm.
The bacteria release a chemical called TBP. The coral senses the chemical and knows if it is the right algae to settle on. Therefore, the coral will only attach to the rock if they receive the proper signal about the coralline algae.
For reef aquarists, live rocks provide a solid surface for the formation of biofilms. Biofilms are communities of cells stuck together by a polymer slime. The polymer includes protection against:
- Changes in Salinity
- UV exposure
- Natural UV antibacterial compounds and predations
However, the biofilm is not a single layer. A mature reef tank has layer upon layer of living biofilm on the rock. Nitrifying bacteria convert ammonia to nitrite and then nitrite to nitrate.
Denitrifying bacteria will remove the nitrate by converting nitrate to nitrogen gas. Other microbes work to recycle a variety of nutrients and organic matter.
A teaspoon of seawater contains about five million bacterial cells. However, lab studies review that about 400 times more bacteria grow on a solid surface than seawater.
Then there are algae, fungi, and protozoans, that live on top of the biofilm. Live rocks are the home base for this microscopic zoo.
You can see that much of the biological filtration in the reef aquarium takes place on the rock. Live rock also provides ledges and crevices to place corals and develop a life-like reef aquarium.
All Natural Reef Rocks Harvested from the Ocean
Before Fiji rocks were banned from export, Fiji rock was the most common type of live rock. This is because it was relatively lightweight and easy to handle.
Fiji rock is usually boat-shipped, which can take up to 30 days to arrive at the supplier's warehouse or fish store must of the marine life on the rock not survive that long journey. Air shipments are possible for this live rock but very expensive.
Tonga Branch is a denser, heavier rock. The antler-like shapes add an interesting dimension to the layout, and it is best to use accent pieces. Pukani dry live rock is from Fiji but is lighter and pores. It is available in larger amounts and is usually stacked to create a stable shelf for corals.
Man-Made Rock Harvested from the Ocean
Acqua-cultured live rocks start as pieces of calcium rocks or artificial rubble. It is scattered in the ocean and left for several years.
Over that time, the rock becomes colonized with marine life and looks like natural rock. Therefore, aquacultured live rock is sustainable and does not harm the reef ecosystem.
It usually comes from the Gulf of Mexico or the Atlantic. If you live in North America, that means it arises fresh and in good condition.
Close Inspection
All lives rocks must be inspected for decay and dead marine life. The farther it traveled, the greater chances it will need to be cured, here is why:
Dead bacteria, sponges, worms, and algae start to decay during shipment. If you place a rock directly into your tank after shipment, chances are very good that the decaying marine life will release harmful ammonia, phosphate, and organics into your water.
Curing live rocks and dry live rocks
- Cure lightly if it is good to live rock
- Cure heavily if there are chances of pests or a lot of decay
- If restarting a tank, heavily cure infested live rock
Use a soft brush to remove any dead surface material poke around in the crevices with a think pick or a pencil to dislodge any crans, worms, or other hitchhikers.
The ideal curing process is to place a live rock in a plastic trash can or a tub filled with saltwater. Heat the water to about &0 degrees Fahrenheit, and add a submersible pump for water movement.
Suppose the rock has a lot of decaying or even months until it is flushed from the rock. Then, if the water smells bad or has high ammonia, you know it's going to take a while to cure.
Some people make a water change every week to remove the excess ammonia. However, if you choose to cure your rock in your aquarium, you will need to make a 100% water change after the cure is complete. And chances are, your water will be yellow and full of algae-promoting nutrients.
The Downside of Live Rock
Many choose to cure rock in a plastics tub instead of the aquarium, which is our recommendation.
There is a downside to starting a reef tank with live rock. No matter how careful you are with the curing process, undesirable marine life will find a way into your tank. Fireworms, bubble algae, and Aiptasia are common pests that sneak into the live rock.
Alternative: Dry Rock
Another option is dry rock. this is dried live rock from the ocean. Even though it is completely dry, it still will leach nutrients and organics as the dead marine life on the rock decays in your water.
It should be cured just like a live rock. So, check the water for ammonia and odors during the curing process.
It will take time for the bare rock to become coated with corals, algae, and biofilm, but over time, it will mature and will look great in the aqaurium
FAQs
How Much Surface Areas is Needed?
Many aquarists get hung up about which rock is more porous or has the most surface area. They are worried there won't be enough surface area to support biological filtration.
The truth is reef aquariums have a very low bioload compared to intensive aquaculture operations. Surface area can be limiting, and fish grow all season, but not in our home aquariums.
That's why we don't need wet-dry filters on reef aquariums. First, however, it is important to understand that the density of the microbial biofilter matches the amount of ammonia, nitrate, and organic nutrients produced in the tank.
More surface area doesn't automatically mean a larger biological filter will form. However, there will be more than enough surface area for nitrification, denitrification, and nutrient recycling, no matter which rock you use.
When the biofilm matures, it bursts to send out microbes to start a new colony. This keeps the biofilter fresh and active at all times.
Biofilms have a life cycle. They don't stay in the same place on the rock. Instead, it is in a constant state of breaking apart and bringing new biofilms.
How Much Rock do I Need?
Well, the answer is not related to the surface area. A lot depends on the design you are looking for. Some like a tank packed with shelves; others live a single pile of rock in the center of the tank. For the typical reef tank with rock piled along the back of the tank, we recommend about one pound per gallon.
Extra rock can be broken up to be placed in a refugium.
Wrapping Up
If you are using dry rock, we recommend sealing a tank with pieces of rubble from another tank or refugium. You can also use a bacterial started product. The best way to get corals and algae started is to scrape some from a piece of rock and disperse it into the new aqaurium.
And, also many coral frags have a coating or Coraline that will also seed the rest of your aquarium. The key to working with live rock is patience. Part of the enjoyment of reef keeping is watching the transformation of a bare tank to a beautiful reef.
If you have to cure the rock, allow for plenty of time to flush out the pores of decays properly. If you go with dry stone, take your time and will enable the rock to become live slowly.
Happy Reefing!
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