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Dry Rock: Curing, Cooking, Bleach, Acid???


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Hey all, I have a request for what I am doing with some Pukani dry rock and thought I would do a little write up. I searched the forums for information and came up with what I believe will be a good method for me.

First lets talk terms. If I am wrong or missed anything let me know. doh.gif

Cooking - This basically means that you are putting your rock in a container with a heater and maybe a powerhead protein skimmer. The idea is to let the bacteria slowly consume the organic material in and on the rock that would cause nitrate and phosphate problems in your tank. Change water as needed. DO NOT ever cook rock in a pot on the stove, this is dangerous for many reasons and is not recommended. Time = 2 months and on. Water = your choice, hose, RO/DI or Saltwater

Curing - This process seems to be exactly like the cooking process to me but can be done in the aquarium if you have no fish or corals in it. The organic material can feed the bacteria and cycle the tank as well but again the time frame could be months before you have low enough nitrates and phosphates for healthy coral. Time = 2 months or more. Water = Saltwater

Bleach - The case with rock like Pukani is it comes with a lot of dried organic material in it, dead sponges, sea stars, etc. According to Randy Holmes-Farley bleach is good at breaking down organic matter. The time frame here is 24 hours in a bleach soak. Rinse the rock and let it dry completely. You could also put fresh water in the container after rinsing and use a product like Seachem Prime to dechlorinate. The concentration of bleach to water is really dependent on how much organic matter is in/on the rock. I used 4 parts water to 1 part bleach but that is really up to you. DO USE personal protective equipment (PPE) when handling chemicals, this means gloves, eye protection, etc. Time = 24 hours plus dry time or dechlorinating

What happens to bleach for the science types: Hint = it turns into salt and oxygen

Though the commercial strength of NaOCl is 12.5% to 15%, the actual delivered product is usually weaker since hypochlorite is unstable and degrades as much as half every 100 days (at 70°F). This degradation accelerates in higher temperatures and in the presence of sunlight. Dilution greatly reduces degradation, especially for solutions delivered in concentrations less than 7% to 8%. The pH of sodium hypochlorite is high because sodium hydroxide is used in its manufacturing process.

NaOCl produces gas as a natural by-product during its decomposition, as much as 1% per day at room temperature. This gas is primarily oxygen; however chlorine gas can also be released at lower pHs.

The decomposition (loss of O2) follows the following reaction:

2NaOCl --> O2 + 2NaCl

Muriatic Acid - The theory behind this is you are going to etch off the first layer of rock that may have phosphates bound up in it. The acid can also help clean off any organic matter that is left on or in the rock. This step is completely optional but if you have to be sure you are not bringing in any unwanted algea or pests it is easy to do. Put your container somewhere outside. Put your rock into a container and fill with water then add the acid. Always put water in first then the acid. Always use PPE when handling chemicals. Put in enough acid to start the rock and water to start bubbling. A heavy foam will form on the surface. If it stops bubbling you can put in more. The time you leave it in is up to you, I have seen 20 minutes to 3 hours. What you want to keep in mind here is that the longer the rock is in the acid bath the more rock will dissolve. You can always do a short acid bath and then if you need more do it again. After you feel it is done you will pour baking soda into the container. This will neutralize the acid, to know for sure if you put in enough you would need to test the PH. I put in enough to get it bubbling then wait about 20 minutes then pour the water out in my backyard. My lawn has never been harmed from this process. Time = 20 minutes to hours depending on your wants and needs

Never mix bleach and acid. It will produce toxic chlorine gas.

Lanthanum Chloride: An optional step you can take once you have the rock in RO/DI water is to check the phosphate level. If it is high you could use lanthanum chloride to help get rid of it faster. You can find this product at pool suppy stores under the name Seaklear phosphate remover or phosfree. You would just add this to the container of rock. It will precipitate the water and turn it white in the presence of phosphate in the water. You can leave this in until you can add and it doesn't turn white anymore. Then you can just drain and clean off the rock. This can work in saltwater, RO/DI or normal tap water. I have read that it works better in saltwater. Also the benifit with that is that you can start the curing process while you are doing this.

My process with dry Pukani:

I first give the rock a good hose down to get obvious organic material off. Then I do the bleach soak. I put 5 3 quart bottles of bleach into 25 gallons of water. This may be overkill however the rock had a strong odor and lots of material on it so it worked for me. I empty the container and rinse off the rock. Now I am letting the rock sit out in the sun until I get some Prime, then I will put them back in water and dechlorinate. After I am satisfied there is no chlorine on the rocks I will fill the container with fresh water and then start the acid bath. Once that is done and I put baking soda on it and wait I will empty the containers and hose off the rocks again. Then I let the rocks dry. Now I will fill up the container with saltwater from my tank water changes and start curing the rock. If phosphate tests high I will add lanthanum chloride. I will add a bacteria like biospira as well as an aquarium heater and power head. I need this rock ready in about 4-6 weeks so I will let it sit until then. I may change some of the water at some point.

This is what has worked for me and the rock had no nuisance algea or pests and had lots of coraline algea on it in about 8 months. The flip side of this is you can not do any of this and maybe be fine as well.

This process could also be used to renew old live rock you have.

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