Curing Rock for Salt Water Aquariums

[Cliff]

Curing Rock for Salt Water Aquariums

This is one topic I spent a lot of time researching before setting up my first SW tank, but I must say, I did not appreciate the importance or the subtleties of curing rock before going through the process first hand. After receiving questions on this topic from other members I thought I would create a thread for this information. Thanks Dave66 for your advice and help with this as well.
I hope I can share a few tips from my lessons learned, and form the helpful advice of others. I am also completing this under the assumption you already have a very basic understanding of a salt water set-up. It would also be helpful if you have already read the sticky on cycling a marine tank, or have already cycled a marine aquarium. This will add another level of detail to the topic, focusing only one live rock. Please keep in mind that as with most aspects of this hobby, there are always different methods to get and maintain a healthy salt water tank. I will only be sharing one of those ways.

Dry (dead) Rock

Basically, it is formed when corals grow and die off, leaving the calcified skeletons. New coral growth develops on top of these structures, and so on. If, at some point, (for many different reasons) the corals and other life forms, and possibly along with beneficial bacteria, die off, the rock structure becomes dead. Once this dead rock is collected from the ocean, it is typically referred to as dry rock (and sometimes base rock).

It’s not always a good idea to just put dry rock into a tank right away. While you “can” do that, it is better to cure / soak the dry rock first. Different vendors have different process for cleaning the rock before storing it to be sold. Some companies will just let the rock to dry out naturally, while others wash the rock with fresh water, and a few will scrub and wash multiple times. Depending on the quality of the rock, and the quality of the cleaning process, dry rock can leach out nitrates and phosphates (from trapped stuff in the pores of the rock) and potentially other trace elements that can lead to less than ideal water quality.


To get your dry rock ready for use in your aquarium, soak it in freshwater about 3 weeks (don’t forget to de-chlorinate). Use a container that is safe for this purpose. I personally prefer to use my quarantine tank for this. Add a power head to the container to get water movement around the rock. After you have your rock soaking for two days, use a fresh water test kit to check the nitrate and phosphate levels. If the nitrate goes higher than 5ppm, or the phosphate goes higher than 1ppm, change at least 50% of the water. Test the water about every second or third day. At the end of each week, change at least 75% of the water. No need for a heater as there is no BB on the dry rock. When your test results come back at a consistent 0ppm for nitrate and phosphates, your rock is now ready to be placed in your aquarium. You can add your soaked (cured) dry rock to your aquarium at any time without risk.

I have personally used this process and it works. After two days the nitrate was somewhere around 5 ppm and there was a phosphate reading (I forgot the exact amount though). This was a small part of the reason why I got almost no algae in my tank during and after the cycle and 5 months later. My tank went right to growing coralline algae.

When picking out dry rock, look for rock that is very porous, almost looking like there is holes part way through it. The more porous it is the better filtration it will provide. Also, look for a uniform almost off- white color. A little discoloration from that is OK.

The below is an example of good quality dry rock.



Below are examples of dry rock to avoid, or use as base rock when stacking rock in your tank. Keep in mind there is nothing wrong with the rocks in these below pics. They, too,will become live rock; they just won’t be able to hold as such beneficial bacteria as more porous rock can.





Just a few pics of how I had cured my dry and live rock. I used my 20 gallon QT for this. I had the power head plugged into a GFI plug to ensure electrical safety. You could also use a HOB filter without any media to get water movement.

[Cliff]

Uncured Live Rock

This is live rock that is relatively freshly harvested from the ocean and filled with all types of life forms, including beneficial bacteria, on it. During the process of collecting it from the ocean and shipping it to the store, or to you, there will be a large die-off giving you a good ammonia spike.The curing process basically allows this die-off to take place naturally without killing off the BB on the rock for filtration. There are a lot of similarities to the cycling process in a fresh water tank. Once cured, your live rock will serve as biological filtration in your marine tank

Curing Live Rock:
When adding uncured live rock to un-cycled marine tanks, the initial ammonia spike from the rock can be used to cycle a tank. However, there is a down side to doing this. It is still possible for “hitch hikers” to survive the process. And remember, not all hitch hikers are good. Also, there will be a fair amount of detritus resulting from the die off. You don’t want that in your tank as it can get in your substrate making it really hard to clean it out. Why would you want this extra work if it is possible to avoid it? This is why (IMO) it is best to cure your live rock outside of your tank if you can.

Curing live rock outside of your tank.
Add your un-cured live rock in a large container and fill with salt water with normal salinity (1.025 to 1.026 specific gravity). Add a power head for water circulation (multiple powers heads would be best). You will also need to keep your water at the same temperature that you will keep it once it is in your tank. Use a heater (s) if required. Cover the container so it is in complete darkness. This is very important to prevent any potential algae like bubble algae. Check your ammonia, nitrites, and nitrates daily with a good quality SW test kit, just as you would for the cycling process. You are basically cycling your live rock during this process. Complete a 20 to 50% water change if your ammonia rises above 2 ppm or the process could be prolonged. Once your ammonia and nitrite readings are 0ppm and your nitrates are decreasing below 20 ppm, your rock is cured and is ready to be added to your tank.

Just make sure you transfer the rock into your tank fully submerged in salt water so there is no noticeable die-off.

Curing rock in your tank:
If you are curing your live rock in your aquarium, follow the same process. Just make sure to clean as much of the detritus out of your substrate and watch for any hitch hikers that might have survived. Do not cure live rock in a set-up tank with fish and/or corals in it.

For my first SW tank, I cured my live rock in my tank. The die off had produced enough ammonia to cycle the tank. Although this did work well for me, I wish I had not done it that way. There was a crab that survived the cycle. This crab was NOT reef safe and ended up damaging some of my corals. I’m still trying to catch this little devil and put him in the live rock compartment of my sump were he can happily live out his days.

When picking out uncured live rock, look for the same qualities as the dry rock. Look for rock that is very porous, almost looking like there are holes though it. The more porous it is the better filtration it will provide. The only difference will be the coloring. There should be at least some coralline algae on it giving it some purple / pink coloring. There might even be some algae on it. Avoid uncured rock that appears to be covered in algae (with almost no coralline) or appears to have a lot of hitch hikers on it. It can be extremely difficult to see hitch hikers in rock, but try your best.

In the below pic, the rock has a lot of algae all over it potentially restricting water flow into the pores of the rock, or potentially helping along a bad algae break-out.



The below photo is a better quality uncured live rock.



I have started curing some live rock for my next reef tank using the same set-up in the above pics with dry rock. As I can put the tank into the shower stall of our downstairs bathroom, I can leave the lights off and the door closed to ensure a completed black-out.

Adding Cured Rock to Your Tank
Never add cured rock to an already cycled tank with fish and/or corals unless you know for a fact it has been shipped and/or transported completely submerged in saltwater without being exposed to the air. This would be the only way you should add cured rock directly to your tank. As almost no local fish stores or their suppliers ship live rock in salt water (due to the cost of shipping the additional weight), you should assume all rock purchased from the store is NOT cured.

As soon as the rock is exposed to the air you will start to get some die-off. Longer exposures to the air will produce a larger amount of die off and higher levels of ammonia. That is why I would suggest you always treat any newly purchased live rock as it was un-cured.

Additionally, some stores mix their cured and uncured live rock together which makes it hard to tell the difference between the fully cured and uncured rock. They could accidently sell you uncured rock thinking it is cured rock.

If you want to add new live rock to an existing tank, you’ll want to make sure it will not cause a mini cycle. If you are not 100% sure the rock was always in saltwater during shipping, you will need to cure it. Set-up a container that is aquarium safe, and fill it with some used tank water (from the set-up you want to add the rock to). Place your new live rock in it with a heater and power head. Test for a mini cycle. You will likely get three possible outcomes with three different sets of steps to take:

If you don’t get a nitrite or ammonia reading after 1 or 2 days, the rock(s) should be safe to add to your existing tank, or if you get a small reading of ammonia (less than 1ppm), leave in the container until the ammonia and nitrites reach 0. Once the levels are both 0 after 1 or 2 days, you can add it to your tank, or if you get an initial ammonia reading of 1 to 2 ppm (or higher) of ammonia, you likely have uncured rock and will need to cure it, following the process for curing rock.


I’ve personally used this process (thank godness) and noticed a small mini-spike (about .25ppm of ammonia) which lasted for about 4 or 5 days. No change in the water parameters in my tank after adding the new cured live rock.

When picking out cured live rock, look for the same qualities as for uncured live rock; look for rock that is very porous, almost looking like there are holes through it. The more porous it is, the better filtration it will provide. The only difference could be the coloring. It should have a darker coloring to it with only very little coralline (if any at all). There should be almost nothing on the rock, no algae, hitch hikers, or anything like that.

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You can see the difference in the two pics of my tank below. The top pic is dry rock, and the bottom pic is the same rock 6 months later, it has become live.

[Rue]

STICKY!

Good article!

[smaug]

Good stuff cliff! You helped me a lot with my little chunk o rock.

[Cliff]

Thanks guys

I'm glad I was able to help Smaug

[ILuvMyGoldBarb]

Great write up cliff. Just one note about the 2 pieces of dry rock you mentioned to avoid. There are reefs where the denser rock is the norm, and if a hobbyist is attempting to create a biotope of one of these regions, that rock would be very desirable. However, that is a very small niche of the reef hobby these days. 99% of hobbyists do need to avoid that denser rock as you mentioned.
Great write up.

[Cliff]

Thanks Goldbarb

You’ve peaked my interest. I'll have to look up regional biotopes. I've heard about but did not realize they would even effect things like you choice of rock. Sounds interesting

[ILuvMyGoldBarb]

Certain reefs around the Caribbean have denser rock. Much of the density of the rock is going to be determined by the coral it was formed from. I've had live rock that was formed from Conch shells, and also from Maze Brains. Both of those pieces are quite dense. In fact, in my 37 right now I have 2 pieces of very dense rock. Each piece probably weighs 25lbs dry.

If you look, Fiji Premium, Tongan Branch, and Key Largo Dry all are quite different in density.

[Surfdog]

Great thread Cliff! It helped me set up my tank that is humming along quite nicely now! I am very happy I have found this wonderful community that is so knowledgable!!! Made my setup effortless

[Millie5]

Good article about these Rocks. Good info for newer.. I am also new, so it's helpful for me.. Hope this info will find helpful for new members and who have limited knowledge like me.