A complete guide to treating synthetic rocks and restoring natural rocks for marine reef aquariums.
Rocks and colonizable substrates in general have always been one of the main drivers of our systems.
In the past, live rock could be relied upon, widely available from shops, wholesalers, and importers, but (fortunately, from an ecological standpoint) increasingly stringent regulations have reduced its importation to the point where it has become virtually impossible to find.
Today, also with a view to reducing anthropogenic impacts, it is preferable to work with inert materials, therefore "synthetic" rocks, natural ones of fossil origin or dead ones from disused aquariums.
Treating rocks before adding them to the aquarium is essential to prevent the release of organic residues or unwanted chemicals and to stabilize water chemistry during a critical phase such as starting a new aquarium.
Untreated inert rocks can release nutrients, metals, production residues, and various other contaminants into the system, which can significantly prolong and make the initial colonization phase of the aquarium very long and difficult.
A few years ago we launched the first experiments with a specific treatment for inert synthetic and natural rocks.
After analyzing the data collected during the prototyping phases, we realized that the process we were using was too complex and laborious to be used effectively by enthusiasts, and would only be usable by industry professionals equipped for this type of work.
We therefore chose to simplify the process, reduce the number of treatments, and use less dangerous, cheaper materials that are more readily available for enthusiasts.
Once we achieved a result comparable to professional treatments, we decided to make the project "open source".
The reduction in extraction from nature, the use of low-impact materials, and the ability to regenerate and recycle natural rocks from disused aquariums have definitively convinced us that the best path was to make it freely accessible to everyone.
This short article offers a simplified protocol for preparing synthetic rocks in two steps, using an acidic citric acid solution and an oxidizing/basic bath with sodium percarbonate.
Why treat synthetic rocks?
Synthetic and natural, reclaimed or quarried rocks represent an ecological and sustainable alternative to live rocks collected in nature.
However, it is very common for these to carry with them heavy metals, chemical residues, contaminants and/or excess nutrients that could severely affect the water parameters and the balance of the system, making maturation extremely long and laborious.
The idea is to bring the material to extreme conditions that will not occur again once the rocks are inserted into the system.
The use of acids, oxidants and bases ensures effective removal of the vast majority of contaminants typically present.
The Three-Phase Treatment Protocol
Phase 1: Citric acid treatment
Acid washing is essential for removing alkaline residues and superficial calcareous deposits from synthetic rocks.
In dead rocks it opens the pores and channels present , physically removing the surface layer, which is generally more contaminated.
Citric acid , a weak organic acid, is safe and readily available, and effective for removing calcareous concretions and clearing blocked channels of coralline debris and other encrusting organisms.
Preparation of the solution:
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Dilute citric acid in RO or demineralized water to obtain a 2.5-5% solution.
This concentration allows for effective cleaning of the first surface layers, without excessively damaging the rock structure.
For a 2.5-5% solution, dissolve 250-500 grams of citric acid in 10 liters of water. -
Completely immerse the rocks in the citric acid solution and let them soak for 12-24 hours , stirring the solution occasionally.
In the case of natural rocks, check that the first surface layer is actually removed.
Generally, a few millimeters are enough, but in the case of particularly contaminated material, it is possible to use a more concentrated solution, leave them to soak for longer, or repeat the soaking.
Cloudiness of the water and partial dissolution of the calcareous material is absolutely normal and is the desired objective.
Check the process regularly to avoid excessive dissolution of material.
In the case of synthetic ceramic rocks, however, you will not observe surface dissolution and the clouding of the water will be greatly reduced.
Don't worry: it's normal. In that case, what we're most interested in is reacting with all the contaminants present within them and the production-related impurities that are sensitive to acid baths.
Intermediate Rinse:
After the acid treatment, a thorough rinse is necessary to remove any residue.
This step is crucial to prevent acid residues from affecting the oxidizing bath.
You can help yourself with a pressure washer or simply using a stiff-bristled brush under running water.
Try to be meticulous and clean the surface as thoroughly as possible.
In this intermediate phase you can use tap water, as long as it is not excessively contaminated.
If you have doubts about the quality of your tap water, don't take any risks and use osmosis or demineralized water.
For best results, or if the rocks are particularly dirty, you can soak them again for another 12-24 hours in reverse osmosis water, taking care to change the water a couple of times.
Phase 2: Treatment with sodium percarbonate
Sodium percarbonate is an extremely versatile compound that serves a dual function in the treatment of synthetic rocks: it acts as an oxidizer , removing any residual organic substances, and as a basic buffer to restore a neutral or slightly alkaline pH.
When dissolved in water, percarbonate releases hydrogen peroxide and sodium carbonate, thus achieving a deep cleansing and pH neutralizing effect.
Preparation of the solution:
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Dilute sodium percarbonate in RO or demineralized water to obtain a 2.5-5% solution.
This concentration allows for effective neutralization of any remaining acid residues, the oxidation of organic residues (nutrient sources) and contaminants sensitive to oxidants.
For a 2.5-5% solution, dissolve 250-500 grams of sodium percarbonate in 10 liters of water. -
The water temperature (around 30-35°C) can speed up the reaction and improve the effectiveness of the solution.
Treatment procedure:
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Immerse the acid-treated rocks in the percarbonate solution and let them soak for 12-24 hours .
This step allows the percarbonate to oxidize any organic residues and, at the same time, stabilize the pH. -
Stir the solution occasionally to optimize contact between the rocks and the solution.
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Any foam production is absolutely normal and is due to the presence of organic residues or residues deriving from the acid bath.
Final rinse:
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After the percarbonate bath, a thorough rinse is essential to eliminate any treatment residues and contaminants still present.
This step ensures that the rocks are ready and safe to place in the aquarium. -
Rinse the rocks thoroughly, this time strictly in osmosis water, using a hard-bristled brush.
If the rocks are particularly dirty or contaminated, you can soak them again for another 12-24 hours in reverse osmosis water, taking care to change the water a couple of times.
Phase 3: EDTA Treatment
EDTA (ethylenediaminetetraacetic acid) is a powerful chelating agent used to bind and remove heavy metals that may be present in synthetic rocks. This step is essential to reduce the risk of toxic elements, such as copper, lead, or zinc, gradually being released into the aquarium, compromising the health of marine organisms.
Preparation of the solution:
- Dissolve 10 g of EDTA in 1 litre of osmotic or demineralised water.
- To ensure a stable and optimal pH (8–9), add 1 teaspoon of baking soda per liter of solution.
- If you have a pH meter, check the values periodically: if the pH drops below 8, add additional bicarbonate in small quantities until it is back in the correct range.
Treatment procedure:
- Immerse the previously rinsed rocks in the EDTA solution and leave them to soak for 48–72 hours.
- To increase the effectiveness of the treatment, keep the solution gently moving using a pump or, alternatively, a simple aerator. This promotes surface water exchange and improves metal chelation.
Final rinse:
Once the treatment is finished, rinse the rocks thoroughly in plenty of osmosis water, preferably changing it a couple of times.
This step is essential to remove all traces of EDTA and the metal complexes formed, making the rocks completely safe for aquarium use.
Drying phase:
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Allow the rocks to air dry in a clean, dry environment.
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After drying, the rocks will finally be ready for introduction into the aquarium .
Additional considerations and precautions:
- Always wear protective gloves and glasses.
- Operate in a well-ventilated area.
- Avoid using products not described in the protocol.
Although we have selected relatively non-hazardous materials, working with acid and oxidizing solutions always requires caution.
It is recommended to wear gloves and protective glasses to avoid accidental contact with chemical solutions and to carry out treatments away from children and animals.
Sodium percarbonate and citric acid, although not dangerous, may release gases or odors, so we recommend always working in a well-ventilated area.
To avoid unnecessary risks or the production of toxic or harmful gases, do not use bleach or other ingredients not described in the protocol.
Advantages of the two-component treatment protocol:
The two-stage treatment with citric acid and sodium percarbonate offers a comprehensive, economical, and reliable approach that ensures the stability of the biological material, effective elimination of the most common unwanted substances present within it, and complete elimination of any production residues.
The treated rocks are therefore ready for long-term integration, contributing to the stability of the system, without altering the water parameters and delicate biological balances.