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Seeding dry rock with live rock

You can seed dry rock with live rock. I have always used live rock in my reef tanks. However, I find that it is also important to add nitrifying bacteria unless you have an abundance of live rock. Keep in mind that there is a risk of introducing nuisance algae and pests to your reef tank from live rock.

Seeding your dry rock with beneficial bacteria is your number one goal.  The bacteria will carry your reef tank through its initial cycle all the way to a stable nitrification machine.  The beneficial bacteria are critical to remove dangerous ammonia and nitrite from the water.  The question is can you seed dry rock with live rock?  The short answer is yes, you can.

Check out my Easy Quick Start Reef Tank Guide to walk you through each step of a new tank setup!

A rock aquascape in a reef tank provides several important functions.  It provides a hiding place for fish and other organisms, it is the substrate that you will attach your corals to, but most importantly, it is a huge portion of where your biological filtration will happen.

Dry rock is white and without any of the established bacteria your reef aquarium will need.  However, it is pest-free and free of any nuisance algae.  It’s inexpensive compared to the other rock choices, and you know you won’t be bringing in any unwanted hitchhikers or algae.  Additionally, it is very porous and great for bacteria colonization.  The downside aesthetically is that it will take months for the rock to change from white to coralline purple.

Don’t be fooled: A man-made dry rock does not have the same surface area as natural dry rock. Know what you are buying!

Nano Reef Adviser

Types of live rock for seeding: Pre-cured live rock is purple and full of coralline algae.  It also comes with an established bacteria bioload that can seed your dry rock.  Unfortunately, you are just as likely to get hitchhiking pests and nuisance algae as well.  You can purchase products like ‘real reef rock,’ cured in saltwater and shipped damp to avoid pests.  The real reef rock also has coralline encrusted but comes pest-free.  Those options cost up to $10.00 per pound, and live rock direct from the ocean is not only difficult to source but isn’t very sustainable environmentally.

The more live rock you can use to seed your dry rock, the better.  The more live rock you have, the faster your tank will go through the nitrogen cycle.  A typical reef tank will have between 1 pound and 1-1/4 pound of rock for each gallon of water.  If half of your rock is established live rock, you will likely have no issue seeding your dry rock fast.

If you have a minimal live rock supply, you can supplement the beneficial bacteria with bacteria starters like Microbacter7 or MicroBacterStart XLM from Brightwell.  It is important to have aerobic and anaerobic microbes to establish the biological filter in a new aquarium.  The bacteria kick-starters like Dr. Tim’s ‘One and Only’ or the Brightwell products are specially designed to provide a full spectrum of microbes for each nitrogen cycle stage.

How to seed dry rock without live rock

To seed dry rock without live rock, you will need to add multiple beneficial bacteria sources for the nitrogen cycle to be successful.  Two methods of seeding dry rock without established live rock add the required aerobic and anaerobic bacteria through live sand and liquid bacteria starter. Both are loaded with nitrifying bacteria. 

Yes, using only dry rock in your reef tank is perfectly acceptable.  However, without using the live rock to help kick off the seeding of the dry rock, you will have to provide the necessary beneficial bacteria differently.

As I mentioned earlier, dry rock is a great product for your aquascape because it is very porous and great for bacteria colonization.  Bacteria will colonize the increased surface area of dry rock as the colonies grow.  The question now is, ‘where do I get the bacteria?’

In a dry rock-only reef tank, I highly recommend using a sand bed substrate.  It is so difficult in the first year to stabilize a reef tank if there is not enough biological filtration.  Everyone I know that has tried to use dry rock with a bare bottom tank has struggled.

If you are going to use dry rock only, I recommend that you use live sand.  Live sand contains a broad spectrum of marine nitrifying bacteria and will help compress new tank cycling time.  The sand’s surface area is immense as a beneficial bacteria playground with all of the different particles.

Additionally, you will want to add bacteria starters like Microbacter7 from Brightwell or Dr. Tims One and Only.  It is important to have aerobic and anaerobic microbes to establish the biological filter in a new aquarium.  The bacteria kick-starters are specially designed to provide both aerobic and anaerobic microbes.  Your nitrogen cycle will be a slow crawl without the additional bacteria.  If you are the super patient type, that might be perfectly ok for you.

Will live sand seed dry rock?

You can seed dry rock with live sand.  I always use live sand in my reef tanks. Live sand is shipped and sold in saltwater and preloaded with live nitrifying bacteria.  As the bacteria colonies grow, they immediately begin to populate the porous dry rock surfaces.  You will want to place between 1 inch to 1.5 inches of live sand over the entire bottom of your tank.  Place the sand in the tank after you have built your dry rock aquascape.  Be sure to choose a particle size that suits your proposed flow rates to avoid sand being blown around the reef tank.

I have cycled many tanks with a combination of live rock and dry rock, and each has been combined with the use of live sand.  I have never had a short circuit in my nitrogen cycles using live sand.  I have also upgraded tanks using new live sand and established live rock from my previous aquarium without issue.

I use CaribSea Arag-Alive Special Grade Reef Sand. It is available online, or you can pick it up at your local fish store. This sand is a grain size that is small enough for your burrowing creatures but not so small that it blows around in the tank.

How long for dry rock to become live?

Dry rock must be seeded with beneficial marine bacteria to become ‘live.’  Three sources of beneficial bacteria for seeding dry rock are established live rock, live sand, and liquid bacteria starters.  The bacteria bonding to the dry rock surface starts within 24 hours.  This is especially true when liquid bacteria products are used. Each type of bacteria reproduces at a different rate, but you can expect a doubling of bacteria numbers every 2-4 days.

How to cure dry rock

There are many types of dry rock, and they come in many different conditions.  I am going to break this down into two general types of dry rock.  The first is the dry rock that has been previously wet and has dead organic material in the rock’s nooks and crannies. The second category of dry rock has been professionally cleaned and dried to ensure no pesky hitchhikers, pests, or algae.  This professionally cleaned dry rock is essentially plug and play and is already free of any organic material.  Therefore it does not require any curing before use.

If you want to avoid the curing period, you can purchase professionally cleaned and dried dry rock in 25-pound boxes.

Before seeding any dry rock that has dead organic material, you will need to cure it.  Curing is a process of getting undesirable organics like dead algae, dead sponges, microfauna, and other undesirable pollutants off the rock’s surface and getting it ready to start a saltwater reef tank.  There are three widely used methods of curing dry rock.  Acid, bleach, or natural curing.

A good candidate for a bleach cure is a rock covered in organic material, whether from the ocean or dried out from an old tank.  A bleach cure is soaking the dry rock in a diluted solution of water and bleach. The bleach will oxidize the organics from the surface of the dry rock and then break them down. This process can be complete within a week in most cases.  Once the cure is complete, rinse the rock and let it dry.

How to cure dry rock with bleach (8 easy steps)

  1. Remove all of the organic material you can get to by hand for a more efficient cure
  2. Most reefers make a solution of one gallon of bleach to ten gallons of water.
  3. Add the bleach to the water, not the water to the bleach, to limit splashing
  4. Add the rock to the solution and then wait about a week
  5. Remove the dry rock from the bin and rinse thoroughly
  6. Rinse the bin thoroughly, add fresh water
  7. Return the dry rock into the fresh water and add an ample de-chlorinator dose to the water.
  8. After 24-48 hours, remove the dry rock and rinse again in RO/DI water.
  9. It’s ready to be placed in your tank!

WARNING:  Bleach is a dangerous chemical.  This article does not provide you the safety precautions or a step-by-step tutorial.  If you want a fast cure using bleach, you will need to commit to doing some research on bleach’s safe handling.  Protecting your face, wearing gloves, and using outside or with ventilation is just a start.

If the use of chemicals is concerning to you, the natural cure method is likely your best choice.

Check out my article for your next step – A low-maintenance reef tank – the EASY way!