An oft heard claim on the forum is that sand substrate is a suboptimal choice because of the potential for growth of anaerobic bacteria, which produce poisonous gases. This information most likely migrated from the world of fishkeeping, as many of us are involved in both hobbies.
Over the years, there has been a quiet revolution regarding the use of sand as a substrate for fish tanks. Reefkeepers employ the deep sandbed as a method of anaerobic filtration, which is beneficial for many invertebrates. Freshwater hobbyists have adopted the technique from reefers. As we have gained a better understanding of the science behind the (fishkeeping) hobby, it is clear that some of the dogmas were founded from a lack of information and fear of catastrophe.
I won't recite the nitrogen cycle in detail, but I'll stress that anaerobic bacteria are an important part of of the denitrification process in nature. As we know, ammonia (and sometimes urea) excreted from amphibians is initially oxidized to nitrite, by way of aerobic bacteria. From this point, nitrite can be further oxidized by different species of aerobic bacteria, converting it into nitrate. Nitrates accumulate in the aquarium, but are considered relatively less-toxic to fish and amphibians. We can deal with high nitrates by doing regular water changes. Therefore, we have adopted the view that aerobic bacteria are good, and anaerobic bacteria are bad for our tanks.
However, in nature, this situation is more complicated. After the nitrite is formed through oxidation of ammonia, anaerobic bacteria reduce (opposite of oxidize) nitrite to harmless nitrogen gas. Excess nitrogen escapes to the atmosphere via diffusion. Without this process, you would see the same build up of nitrates in natural settings. Through the reduction process, methane and sometimes sulfide gases are produced. The anaerobic colonies are visible as a dark layer in the sand, and are sometimes accompanied by methane bubbles. In nature, these gas bubbles are slowly released from the substrate, and they do not normally pose a problem to fish or amphibians. In the aquarium, it is feared that a giant bubble of methane will be released from the substrate and kill everything in it's path (as read by the movie preview voice).
What I want to explore is whether sand substrates are actually fostering anaerobic bacteria at densities required to harm amphibians in captivity. It seems to me that most of us maintain aquatic amphibians with at least some live plants, which limit the amount of nutrients processed by anaerobic bacteria. Also, we do regular water changes, do not keep the animals in crowded conditions, and have at least a bubbler to keep oxygen levels normal. So, who among us has had an amphibian suffer from conditions directly attributable to anaerobic bacteria in the substrate? Is the advice coming from experience or from fear?
It has been my experience that the deep sandbed provides a MORE stable environment, by allowing nutrients to be processed through multiple pathways, preventing the nitrite swings that can stress animals. However, this experience is based on fishtanks, as all of my newts remain in bare bottom tanks... Because I'm scared.
Over the years, there has been a quiet revolution regarding the use of sand as a substrate for fish tanks. Reefkeepers employ the deep sandbed as a method of anaerobic filtration, which is beneficial for many invertebrates. Freshwater hobbyists have adopted the technique from reefers. As we have gained a better understanding of the science behind the (fishkeeping) hobby, it is clear that some of the dogmas were founded from a lack of information and fear of catastrophe.
I won't recite the nitrogen cycle in detail, but I'll stress that anaerobic bacteria are an important part of of the denitrification process in nature. As we know, ammonia (and sometimes urea) excreted from amphibians is initially oxidized to nitrite, by way of aerobic bacteria. From this point, nitrite can be further oxidized by different species of aerobic bacteria, converting it into nitrate. Nitrates accumulate in the aquarium, but are considered relatively less-toxic to fish and amphibians. We can deal with high nitrates by doing regular water changes. Therefore, we have adopted the view that aerobic bacteria are good, and anaerobic bacteria are bad for our tanks.
However, in nature, this situation is more complicated. After the nitrite is formed through oxidation of ammonia, anaerobic bacteria reduce (opposite of oxidize) nitrite to harmless nitrogen gas. Excess nitrogen escapes to the atmosphere via diffusion. Without this process, you would see the same build up of nitrates in natural settings. Through the reduction process, methane and sometimes sulfide gases are produced. The anaerobic colonies are visible as a dark layer in the sand, and are sometimes accompanied by methane bubbles. In nature, these gas bubbles are slowly released from the substrate, and they do not normally pose a problem to fish or amphibians. In the aquarium, it is feared that a giant bubble of methane will be released from the substrate and kill everything in it's path (as read by the movie preview voice).
What I want to explore is whether sand substrates are actually fostering anaerobic bacteria at densities required to harm amphibians in captivity. It seems to me that most of us maintain aquatic amphibians with at least some live plants, which limit the amount of nutrients processed by anaerobic bacteria. Also, we do regular water changes, do not keep the animals in crowded conditions, and have at least a bubbler to keep oxygen levels normal. So, who among us has had an amphibian suffer from conditions directly attributable to anaerobic bacteria in the substrate? Is the advice coming from experience or from fear?
It has been my experience that the deep sandbed provides a MORE stable environment, by allowing nutrients to be processed through multiple pathways, preventing the nitrite swings that can stress animals. However, this experience is based on fishtanks, as all of my newts remain in bare bottom tanks... Because I'm scared.