Acid curing is the most aggressive method of curing rock. It is also the least safe among the accepted methods of how to cure live rock for a reef tank or saltwater aquarium. There are very few instances in which we consider acid curing a necessity over a bleach or natural live rock cure.

We will answer three direct questions about curing the rock for your reef aquarium using muriatic acid.

 

  • 1. What is an acid cure?
  • 2. When is it appropriate to acid cure rock?
  • 3. How to cure rock with acid correctly?

 

Muriatic Acid and Dry Rock

 

Many people think acid will attack or dissolve organic material that is on the rock but in reality the acid cure process is very quick and effectively breaking down organic material in such a short time is not likely to happen to the degree that you need it too.

 

What actually happens is the acid will immediately start dissolving the surface of the calcium carbonate based rock, essentially removing the top layer. So instead of dissolving or breaking down the organic material itself, the acid is removing the top layer of rock this organic material may be attached too. More importantly, it will also remove any elements that may be bound up in this top layer of rock such as phosphorus.

 

Muriatic Acid Warning Label

 

To Cure or Not to Cure...with Acid

Considering the safety risks of working with acid along with the hassle involved in clean-up, it is almost never the recommended solution with one specific exception.

 

There is certainly no need to acid cure wet live rock that is full of beautiful coralline algae, there is no need to do it with clean mined rock like Marco Rocks Reef Saver and no reason to do it with man-made rocks like Real Reef and Caribsea Life Rock. In these instances, if a cure is required a natural cure or curing with bleach is a far better option.

 

Even with ocean based dry rock where there is a lot of dead organic material to be removed, a bleach cure is more economical, effective and arguably safer.

 

Bleach Cure Results

 

In fact, when BRStv investigated the three methods of curing rock to see which method is most effective in terms of removing organics, the bleach cure out-performed an acid cure.

If it is so risky, why do it?

The only instance we recommend the use of acid for curing is with rock that came from a failed tank. In addition to the organic material attached to the rock, this used rock often contains bound up phosphate inside the rock’s surfaces that could leach out if placed into an aquarium which will contribute to algae blooms and general degradation of the environment for your fish and corals.

 

Dry Rock

 

Dissolving the top layer of rock will get rid of bound up elements and after a thorough rinse, many reefers continue the process with a bleach cure to get rid of any leftover organic material attached after the acid wash.

 

Steps to Curing Dry Rock with Acid

 

 

How to Acid Cure Live Rock

 

Step #1 - Safety first! If you do not already know proper safety techniques and procedures for dealing with strong acids, skip this project. Acid can burn or blind you and anyone near you, as well as damage property. The benefits versus other methods are not worth the risk or the amount of time to learn how to do this safely.

 

Safety Gear

 

Essential Safety Gear

  • Arm length protective gloves
  • Protective Goggles or appropriate eye protection
  • Ventilator/gas mask
  • Black Plastic Sheet
  • Baking Soda; 2-3 boxes or more

 

WARNING! - The process must be done outdoors, not in a basement or garage. Outside, the gases can dissipate quickly and won’t be a health hazard to you or your family. There is also a good chance the container may overflow which will make a mess and damage the surrounding area. On that note, laying down a thick plastic sheet over the area is highly recommended along with keeping some acid neutralizer on hand such as baking soda.

 

Brute Trash Can Outside

 

Step #2 - Find a container (Brute trash can) which is large enough to hold all of your rock, bring it outside and fill it with water. Most reefers like to use purified RO/DI water but in this case tap water is a suitable alternative.

 

Hobby Ratio of Water to Acid

 

Step #3 - Once you have filled it with water, add Muriatic Acid which can be found at most hardware stores. The unofficial hobby recommendation is a 10:1 mix, meaning for every 10 gallons of water, add 1 gallon of acid.

 

During our BRStv Investigates experiment, we also tested a more dilute solution with a 20:1 ratio of water to acid and found it to be more appropriate for our application because the more concentrated mix dissolved too much rock material within the necessary soaking time.

 

The thing to consider here isn’t really a ratio of water to acid, rather the ratio of rock to acid. The water is simply a carrier and helps make the process easier and safer. The rock is acting as a buffer to the acid so the more rock you have to clean, the more acid you will need to get the job done.

 

Rock in curing bin

 

As the solution becomes more concentrated, it will dissolve more rock material in the given time and you certainly run the risk of dissolving too much if you have too much acid or not enough rock.

 

This isn’t an exact science; there is not a universally agreed upon acid to water or acid to rock ratio and it probably changes between rock types and densities. Researching and discussing the acid was method for curing live rock with others who have done it, will prove to be invaluable.

 

BRS Water to Acid Ratio

 

Based on our experiments, we recommend that you start with a 20:1 water to muriatic acid ratio for every 15 pounds of rock. Keep in mind you can always add more but never less and the more rock you have to cure, the more acid will be required to get the job done.

When diluting the acid make sure the water is in the storage container and you add acid to water and not the reverse. Adding water to acid can cause all kinds of dangerous reactions as well as splash concentrated solution much easier.

 

Acid foaming on rock in Brute trash can

 

Step#4 - Make sure you are wearing your safety gear and slowly lower your rock into the container. It will immediately start to foam and there is a very good chance it will foam over the sides. That foam can damage your driveway or lawn so make sure you have some thick plastic down and a few boxes of baking soda around to neutralize it if needed.

 

Step #5- Wait 15 minutes and let the acid do it’s work and then dump in a bunch of baking soda to neutralize the reaction and stop it from dissolving more of the rock. How much baking soda will depend on how much acid you used.

 

Cured rock in Brute Trash Can

 

Step #6 - Move the rock to a new bin and rinse it thoroughly with freshwater. I might even add a box of baking soda to the first freshwater rinse just to be sure any remaining acid is neutralized.

 

Once you are confident the rock as been thoroughly rinsed, let it dry out, Next, you can either bleach or natural cure the rock to remove any remaining organics or just start the cycle if you feel the rock is clean enough.

 

Bleach and Acid Cure Results

 

In our experiments the acid cure followed by a thorough freshwater rinse and then a separate bleach cure produced the best overall results for removing dead organic material and locked up elements.