SludgeMunkey
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Use of Limestone in Aquatic Vivaria
The use of naturally occurring limestone products and related rock in vivaria is probably one of the most controversial aspects of vivaria building. The internet and many publications provide much conflicting and incorrect information on the use of this class of rock. Here we will attempt to present facts in the attempt to allow a responsible hobbyist to draw their own conclusions. A basic working knowledge of high school chemistry is required to fully grasp the concepts presented.
What is Limestone?
In its ideal form, limestone is a naturally occurring form of various carbonates deposited through biological and geochemical action into a dense form of sedimentary rock. The primary component is various forms of calcium carbonate (CaCO3) most commonly in the form of diatomaceous microfossils. By definition, limestone is comprised of at least 50% CaCO3. Forms of limestone go by many different names such as aragonite, calcite, travertine, tufa and numerous localized names.
As a result of the various names for this naturally occurring CaCO3, identification can be difficult for the novice. Generally speaking, the presence of fossils is a good indicator, however many other forms of rock contain fossils. A sure fire method to identify limestone is to break a small “fresh face” somewhere on the sample and then place a few drops of hydrochloric acid solution (HCl) on the break. If energetic effervescence (seriously active fizzing) is observed, the rock is positive for the presence of CaCO3.
Aragonite (limestone made up of sea shell and coral fragments) should never be used in freshwater enclosures. Travertine and tufa should never be used due to the high probability of toxic minerals incorporated in the stone.
Vinegar (acetic acid solution CH3COOH) should NOT be utilized as a test reagent for limestone as the reaction is significantly less active than HCl. This particular reaction is such that air escaping from porous stone can look like a vinegar “fizz”. Consumer grade HCl solutions can be easily purchased at pet stores in the form of a product named “pH Down” or at swimming pool and spa suppliers as “muriatic acid”. The author highly recommends the use of splash resistant goggles, a face shield, and acid resistant disposable gloves when working with acids.
Additionally, limestone can contain inclusions of numerous other carbonates and minerals. Dolomite [CaMg(CO3)2], a naturally occurring magnesium carbonate is most common. Various forms of iron (rust, FeO and Fe2O3) and iron sulfides (pyrites, FeS2 being most common) are also often found. The presence of silica sands, clay, and even quartzite is extremely common.
A number of these inclusions can be extremely harmful to live amphibians, fish and mollusks in vivaria. Dolomitic limestone is acceptable, however caution should be exercised as these forms often contain pyrites. Any rock that obviously contains metallic crystals or rust should not be used in vivaria.
Understanding Water Chemistry and Limestone
One of the most important aspects on deciding if limestone is suitable for use in your vivarium is your water chemistry. A working knowledge of your water chemistry as it comes from the source is an absolute must! If you utilize municipal tap water, this is easy to do as most, if not all locales, require an annual water quality report by law. For hobbyists that utilize well or bottled water, it is advisable that effort is put forth to do extensive testing or have testing professionally done. Total hardness, carbonate hardness, dissolved O2, and TDS (total dissolved solids) should be noted. Salinity (presence of salts) is also important, especially for systems with inline water softeners.
Calcium carbonate in the form of limestone is soluble in water and therefore readily dissolves over time. The amounts of carbonates present in conjunction with temperature directly affect the pH and dissolved oxygen (O2) in your enclosure. This is the source of much argument and misguided information in the aquarium hobby. The truth is: Cold water readily holds more oxygen than warm. The amount of dissolved oxygen is directly affected by the pH of the water. Low pH, warm water has low dissolved O2. Cold, higher pH water has higher dissolved oxygen. Likewise levels of dissolved CO2 are affected.
The addition of limestone to an established tank or pond (which tends to be on the lower end of acceptable water quality ranges) can cause a wild change in pH. This in turn can result in uncontrolled changes in the amount of oxygen and carbon dioxide in the water. While these fluctuations may seem miniscule, the effects on the nitrogen cycle are exponential.
These changes can be fatal to the bacteria that maintain the ammonia, nitrate, and nitrite levels. Destroy any part of the nitrogen cycle and deadly ammonia spikes are guaranteed. This results, more often than not, in dead pets or specimens with compromised immune systems. This is often called a “tank crash” in the hobby. As a result, limestone should only be used in new enclosure builds.
Additionally, the presence of salts from water softeners can also react with limestone to cause the previously mentioned disasters. These “water softeners” utilize ion exchange to “swap” calcium ions with salt ions. This makes for less damage to your plumbing and appliances, but results in adverse conditions for your pets. These salts can become highly concentrated over time in an enclosure. Eventually, the ion “swap” between the salt in the water and the calcium in the limestone can cause a tank crash.
In short, hard tap water is acceptable to use with limestone. Soft water is not unless the rock is sealed. Lower pH (below 7ph) water is not suitable for use with limestone. Higher pH (7.5-9pH) water is. Do your research. Know your water and as with any vivaria project,” When in doubt, leave it out!”
The type of pet the enclosure is intended for is also very important. Generally speaking, limestone should only be used with species that inhabit bodies of water supplied by streams and springs in areas that have high occurrences of limestone. This rock should never be used with soft-water tropical, or species that utilize vernal pools and swamps.
Selecting and Preparing Limestone
Once you have determined if limestone is right for your application, you must select the rock and prepare it for use. The general rules for selecting vivaria additions apply here too! Never get rock from areas or businesses that have the risk of contamination with fertilizers, pesticides, or herbicides. If you are unsure of the risk of contamination, go somewhere else.
When collecting your own, never take rock without permission from the land owner. Be aware of local and national laws. Some areas require permits or ban collecting altogether. Do not destroy the habitats of wild organisms. Always carefully check your rocks for hitchhikers! It is best to have a small amount of test acid with you to properly identify your find in the field. A good field guide or local geology report can be handy too! Only take what you can use.
When purchasing limestone, generally it is already identified for you. However, use caution as many rock suppliers’ products have been acid washed or chemically treated for landscaping and construction use. Additionally, carelessness at the retail outlet can lead to contamination from a huge range of toxic chemicals such as lawn fertilizers and pressure treated wood. As limestone is readily absorbent, these sources are inadvisable to the hobbyist.
Once you have acquired your rock, remove sharp edges and points with a coarse file or rasp, or a rotary tool like a Dremel. Remove foreign particulates, dirt, vegetation and the like as much as possible. A stiff nylon brush and some compressed or “canned” air are helpful here. Attempt to remove limestone dust and crumbling areas that could foul your filter equipment or choke your pets.
Now, place your limestone in a clean five gallon bucket and submerge it in white distilled vinegar overnight. The weak effervescent action will help to further dislodge dirt and grime. It can also show you weak areas of the rock that could become hazardous to your pets later. Rinse the rock well with tap water and then sterilize it by one of the following methods: Boiling, Baking, or treatment with Hydrogen peroxide.
Boiling is the safest and most effective method. Limestone boiled in tap water for roughly an hour per kilogram is ideal. The larger the sample, the longer you should boil it. A pressure cooker significantly speeds the process. Baking at 121°C is also suitable, but the risk of the rocks fracturing and even “exploding” is high. A hydrogen peroxide bath works well, but is only useful for small rocks given the expense of the amount of peroxide needed. The use of household bleach and/or ammonia is absolutely NOT an option at any time when working with carbonates.
If the limestone is to be used in an enclosure with soft water, it is advisable to seal the entire surface with a clear urethane sealant rated for use with porous surfaces. This is really not the best course of action though, as it is impossible to completely seal the rock. Again it must be stated that the use of limestone with soft water is an extremely poor idea!
Installation of Limestone in Vivaria
Once the rock is prepared, cleaned, and sanitized it is ready for use. Care should be used as limestone is heavy. It can also scratch glass and acrylic enclosures.
Limestone should be laid out in such a way that makes for easy cleaning of the enclosure. Planning ahead is paramount. One of the huge risks with using real rock in an enclosure is the crushing hazard to the animals. The rock should be secured to prevent shifting or collapse.
Silicone adhesives are ill suited for the task, as they do not adhere well to limestone. Aquaculture rated epoxy putties are ideal as are water activated urethane glues. The use of small sections of PVC pipe to balance and stabilize rocks is also advisable. Care must be taken to allow from cleaning and removal. In other words, don’t overdo it! Use only enough adhesive to make it safe without hindering the need for removal in the future.
Once the enclosure build is complete, cycle the water as normal. Allow plenty of time to get the nitrogen/ammonia cycle stabilized. Ideally, a 60 to 90 day cycle time is best. Cycle it without plants the first month, testing water chemistry weekly. Add plants, wood and other decorations slowly over the next month, still testing weekly. For the final thirty days, continue to test weekly to verify stability.
Be aware that as when using any natural product in a vivarium, it will support the growth of algae and bacteria. While in most cases this is not an issue, it can lead to problematic tank maintenance and eventual cycle crash. Regular water testing is essential in natural aquaria.
The use of naturally occurring limestone products and related rock in vivaria is probably one of the most controversial aspects of vivaria building. The internet and many publications provide much conflicting and incorrect information on the use of this class of rock. Here we will attempt to present facts in the attempt to allow a responsible hobbyist to draw their own conclusions. A basic working knowledge of high school chemistry is required to fully grasp the concepts presented.
What is Limestone?
In its ideal form, limestone is a naturally occurring form of various carbonates deposited through biological and geochemical action into a dense form of sedimentary rock. The primary component is various forms of calcium carbonate (CaCO3) most commonly in the form of diatomaceous microfossils. By definition, limestone is comprised of at least 50% CaCO3. Forms of limestone go by many different names such as aragonite, calcite, travertine, tufa and numerous localized names.
As a result of the various names for this naturally occurring CaCO3, identification can be difficult for the novice. Generally speaking, the presence of fossils is a good indicator, however many other forms of rock contain fossils. A sure fire method to identify limestone is to break a small “fresh face” somewhere on the sample and then place a few drops of hydrochloric acid solution (HCl) on the break. If energetic effervescence (seriously active fizzing) is observed, the rock is positive for the presence of CaCO3.
Aragonite (limestone made up of sea shell and coral fragments) should never be used in freshwater enclosures. Travertine and tufa should never be used due to the high probability of toxic minerals incorporated in the stone.
Vinegar (acetic acid solution CH3COOH) should NOT be utilized as a test reagent for limestone as the reaction is significantly less active than HCl. This particular reaction is such that air escaping from porous stone can look like a vinegar “fizz”. Consumer grade HCl solutions can be easily purchased at pet stores in the form of a product named “pH Down” or at swimming pool and spa suppliers as “muriatic acid”. The author highly recommends the use of splash resistant goggles, a face shield, and acid resistant disposable gloves when working with acids.
Additionally, limestone can contain inclusions of numerous other carbonates and minerals. Dolomite [CaMg(CO3)2], a naturally occurring magnesium carbonate is most common. Various forms of iron (rust, FeO and Fe2O3) and iron sulfides (pyrites, FeS2 being most common) are also often found. The presence of silica sands, clay, and even quartzite is extremely common.
A number of these inclusions can be extremely harmful to live amphibians, fish and mollusks in vivaria. Dolomitic limestone is acceptable, however caution should be exercised as these forms often contain pyrites. Any rock that obviously contains metallic crystals or rust should not be used in vivaria.
Understanding Water Chemistry and Limestone
One of the most important aspects on deciding if limestone is suitable for use in your vivarium is your water chemistry. A working knowledge of your water chemistry as it comes from the source is an absolute must! If you utilize municipal tap water, this is easy to do as most, if not all locales, require an annual water quality report by law. For hobbyists that utilize well or bottled water, it is advisable that effort is put forth to do extensive testing or have testing professionally done. Total hardness, carbonate hardness, dissolved O2, and TDS (total dissolved solids) should be noted. Salinity (presence of salts) is also important, especially for systems with inline water softeners.
Calcium carbonate in the form of limestone is soluble in water and therefore readily dissolves over time. The amounts of carbonates present in conjunction with temperature directly affect the pH and dissolved oxygen (O2) in your enclosure. This is the source of much argument and misguided information in the aquarium hobby. The truth is: Cold water readily holds more oxygen than warm. The amount of dissolved oxygen is directly affected by the pH of the water. Low pH, warm water has low dissolved O2. Cold, higher pH water has higher dissolved oxygen. Likewise levels of dissolved CO2 are affected.
The addition of limestone to an established tank or pond (which tends to be on the lower end of acceptable water quality ranges) can cause a wild change in pH. This in turn can result in uncontrolled changes in the amount of oxygen and carbon dioxide in the water. While these fluctuations may seem miniscule, the effects on the nitrogen cycle are exponential.
These changes can be fatal to the bacteria that maintain the ammonia, nitrate, and nitrite levels. Destroy any part of the nitrogen cycle and deadly ammonia spikes are guaranteed. This results, more often than not, in dead pets or specimens with compromised immune systems. This is often called a “tank crash” in the hobby. As a result, limestone should only be used in new enclosure builds.
Additionally, the presence of salts from water softeners can also react with limestone to cause the previously mentioned disasters. These “water softeners” utilize ion exchange to “swap” calcium ions with salt ions. This makes for less damage to your plumbing and appliances, but results in adverse conditions for your pets. These salts can become highly concentrated over time in an enclosure. Eventually, the ion “swap” between the salt in the water and the calcium in the limestone can cause a tank crash.
In short, hard tap water is acceptable to use with limestone. Soft water is not unless the rock is sealed. Lower pH (below 7ph) water is not suitable for use with limestone. Higher pH (7.5-9pH) water is. Do your research. Know your water and as with any vivaria project,” When in doubt, leave it out!”
The type of pet the enclosure is intended for is also very important. Generally speaking, limestone should only be used with species that inhabit bodies of water supplied by streams and springs in areas that have high occurrences of limestone. This rock should never be used with soft-water tropical, or species that utilize vernal pools and swamps.
Selecting and Preparing Limestone
Once you have determined if limestone is right for your application, you must select the rock and prepare it for use. The general rules for selecting vivaria additions apply here too! Never get rock from areas or businesses that have the risk of contamination with fertilizers, pesticides, or herbicides. If you are unsure of the risk of contamination, go somewhere else.
When collecting your own, never take rock without permission from the land owner. Be aware of local and national laws. Some areas require permits or ban collecting altogether. Do not destroy the habitats of wild organisms. Always carefully check your rocks for hitchhikers! It is best to have a small amount of test acid with you to properly identify your find in the field. A good field guide or local geology report can be handy too! Only take what you can use.
When purchasing limestone, generally it is already identified for you. However, use caution as many rock suppliers’ products have been acid washed or chemically treated for landscaping and construction use. Additionally, carelessness at the retail outlet can lead to contamination from a huge range of toxic chemicals such as lawn fertilizers and pressure treated wood. As limestone is readily absorbent, these sources are inadvisable to the hobbyist.
Once you have acquired your rock, remove sharp edges and points with a coarse file or rasp, or a rotary tool like a Dremel. Remove foreign particulates, dirt, vegetation and the like as much as possible. A stiff nylon brush and some compressed or “canned” air are helpful here. Attempt to remove limestone dust and crumbling areas that could foul your filter equipment or choke your pets.
Now, place your limestone in a clean five gallon bucket and submerge it in white distilled vinegar overnight. The weak effervescent action will help to further dislodge dirt and grime. It can also show you weak areas of the rock that could become hazardous to your pets later. Rinse the rock well with tap water and then sterilize it by one of the following methods: Boiling, Baking, or treatment with Hydrogen peroxide.
Boiling is the safest and most effective method. Limestone boiled in tap water for roughly an hour per kilogram is ideal. The larger the sample, the longer you should boil it. A pressure cooker significantly speeds the process. Baking at 121°C is also suitable, but the risk of the rocks fracturing and even “exploding” is high. A hydrogen peroxide bath works well, but is only useful for small rocks given the expense of the amount of peroxide needed. The use of household bleach and/or ammonia is absolutely NOT an option at any time when working with carbonates.
If the limestone is to be used in an enclosure with soft water, it is advisable to seal the entire surface with a clear urethane sealant rated for use with porous surfaces. This is really not the best course of action though, as it is impossible to completely seal the rock. Again it must be stated that the use of limestone with soft water is an extremely poor idea!
Installation of Limestone in Vivaria
Once the rock is prepared, cleaned, and sanitized it is ready for use. Care should be used as limestone is heavy. It can also scratch glass and acrylic enclosures.
Limestone should be laid out in such a way that makes for easy cleaning of the enclosure. Planning ahead is paramount. One of the huge risks with using real rock in an enclosure is the crushing hazard to the animals. The rock should be secured to prevent shifting or collapse.
Silicone adhesives are ill suited for the task, as they do not adhere well to limestone. Aquaculture rated epoxy putties are ideal as are water activated urethane glues. The use of small sections of PVC pipe to balance and stabilize rocks is also advisable. Care must be taken to allow from cleaning and removal. In other words, don’t overdo it! Use only enough adhesive to make it safe without hindering the need for removal in the future.
Once the enclosure build is complete, cycle the water as normal. Allow plenty of time to get the nitrogen/ammonia cycle stabilized. Ideally, a 60 to 90 day cycle time is best. Cycle it without plants the first month, testing water chemistry weekly. Add plants, wood and other decorations slowly over the next month, still testing weekly. For the final thirty days, continue to test weekly to verify stability.
Be aware that as when using any natural product in a vivarium, it will support the growth of algae and bacteria. While in most cases this is not an issue, it can lead to problematic tank maintenance and eventual cycle crash. Regular water testing is essential in natural aquaria.