This is a rather old paper and the plant is rather slow growing.
However, the study was done well and details out the effects and issues surrounding aquatic plant roots and O2.
Please read:
http://www.plantphysiol.org/cgi/reprint/105/3/847.pdf
Most of the proponents of heating cables or large pumice underlayments, "pseudo plenums" have suggested, and I might add........ without any evidence for support (if you have seen any real data, please contact me, because I've never seen any to date after looking for 20+ years)....that their products increase circulation and bring O2 to the anaerobic sediments below thereby enhancing plant root development/growth.
It might help for aquarists to take a step back first and ask the question:
What about the sediment that causes low O2 to begin with?
1. There must be some organic carbon source in the sediment for aerobic bacteria to consume, otherwise the O2 levels will remain the same as the water column.
This is obvious and testable, if there is nothing consuming O2 in the sediment, say plain sand, it does not matter how deep it is............the rate of consumption is essentially zero, so O2 can move in without being depleted.
Typically, in a new aquarium, there is no organic matter in the sediment unless soil or ADA AS, and other amendments are added.
2. Plants are not static, they will actively alter their environment. Aquatic plants are very well understood to act like "pipes", pumping O2 into the anoxic sediments. Given good light, CO2 and nutrients, they can do this amazingly well.
This is natural process and needs no amplification. By adding O2 to the root zone, they effectively grow various species of bacteria that aid in the nutrient uptake and remove the need to add more circulation to the root zone.
3. Algae are not limited by nutrients in the water column(Fe, NO3, PO4, K+), thus even if you ascribe to this theory, adding more circulation would conflict with this theory by allowing higher rates of nutrients to leach out.
4. Grain size also plays a large role if any diffusion process in sediments. Over time, the grain size pore spaces are reduced and smaller grains migrate to the lower zones while large grains migrate to the top layer. Thus adding larger layers on the bottom will often not last over time. Pool and water sand filters use larger grains going to smaller grains from top to bottom as well for this very reason to aid in filtering. The sediment acts in a similar, although slower process, slowly clogging over time. Plants respond by adding O2 and growing more roots. The aquarist can deep vacuum once a year as well, or uproot and replant areas every few months, years as needed as well. Cables and other diffusion aids will increase the rate of clogging, not aid in plant growth.
5. Are plant roots O2 limited to the point it limits growth in aquatic sediments?
And if so, does adding flow, via cables or larger grains improve this in a significant way? These questions have never been answered.
Read the article, think about aquatic plant roots, think about faster growing species in warmer temperatures and how that might affect the zone of O2 around plant roots, think about how a large sword plant or Crypt might influence the sediment with massive root systems, then remove the plant and predict what you might expect.
By ignoring the plant roots' role in the process, as well as the pore size through time, it really appears to be based on marketing, not on plant growth or research.
I talk to Claus from Tropica many years ago, as well as Troels and Ole recently about all this. They know of nothing that suggest the plants grow better using these two methods. Havign set up numerous aquariums with and without both methods, I've yet to see any evidence that they do as claimed.
ADA's Power Sand appears to be a hold over from that time in history when the cables where popular, and the idea that adding nutrients to the root zone would limit algae. Dupla had already done 1/2 the marketing for you and PS is cheaper than cables. At least PS does add some nutrients.
Still, nutrients can be added without the PS altogether.
Thus we see no differences in growth without PS when the same nutrients are added back. Which mirrors the observations.
More reading on this topic and N's role:
Cookie Absent
Archaea Dominate the Ammonia-Oxidizing Community in the Rhizosphere of the Freshwater Macrophyte Littorella uniflora -- Herrmann et al. 74 (10): 3279 -- Applied and Environmental Microbiology
Regards,
Tom Barr
However, the study was done well and details out the effects and issues surrounding aquatic plant roots and O2.
Please read:
http://www.plantphysiol.org/cgi/reprint/105/3/847.pdf
Most of the proponents of heating cables or large pumice underlayments, "pseudo plenums" have suggested, and I might add........ without any evidence for support (if you have seen any real data, please contact me, because I've never seen any to date after looking for 20+ years)....that their products increase circulation and bring O2 to the anaerobic sediments below thereby enhancing plant root development/growth.
It might help for aquarists to take a step back first and ask the question:
What about the sediment that causes low O2 to begin with?
1. There must be some organic carbon source in the sediment for aerobic bacteria to consume, otherwise the O2 levels will remain the same as the water column.
This is obvious and testable, if there is nothing consuming O2 in the sediment, say plain sand, it does not matter how deep it is............the rate of consumption is essentially zero, so O2 can move in without being depleted.
Typically, in a new aquarium, there is no organic matter in the sediment unless soil or ADA AS, and other amendments are added.
2. Plants are not static, they will actively alter their environment. Aquatic plants are very well understood to act like "pipes", pumping O2 into the anoxic sediments. Given good light, CO2 and nutrients, they can do this amazingly well.
This is natural process and needs no amplification. By adding O2 to the root zone, they effectively grow various species of bacteria that aid in the nutrient uptake and remove the need to add more circulation to the root zone.
3. Algae are not limited by nutrients in the water column(Fe, NO3, PO4, K+), thus even if you ascribe to this theory, adding more circulation would conflict with this theory by allowing higher rates of nutrients to leach out.
4. Grain size also plays a large role if any diffusion process in sediments. Over time, the grain size pore spaces are reduced and smaller grains migrate to the lower zones while large grains migrate to the top layer. Thus adding larger layers on the bottom will often not last over time. Pool and water sand filters use larger grains going to smaller grains from top to bottom as well for this very reason to aid in filtering. The sediment acts in a similar, although slower process, slowly clogging over time. Plants respond by adding O2 and growing more roots. The aquarist can deep vacuum once a year as well, or uproot and replant areas every few months, years as needed as well. Cables and other diffusion aids will increase the rate of clogging, not aid in plant growth.
5. Are plant roots O2 limited to the point it limits growth in aquatic sediments?
And if so, does adding flow, via cables or larger grains improve this in a significant way? These questions have never been answered.
Read the article, think about aquatic plant roots, think about faster growing species in warmer temperatures and how that might affect the zone of O2 around plant roots, think about how a large sword plant or Crypt might influence the sediment with massive root systems, then remove the plant and predict what you might expect.
By ignoring the plant roots' role in the process, as well as the pore size through time, it really appears to be based on marketing, not on plant growth or research.
I talk to Claus from Tropica many years ago, as well as Troels and Ole recently about all this. They know of nothing that suggest the plants grow better using these two methods. Havign set up numerous aquariums with and without both methods, I've yet to see any evidence that they do as claimed.
ADA's Power Sand appears to be a hold over from that time in history when the cables where popular, and the idea that adding nutrients to the root zone would limit algae. Dupla had already done 1/2 the marketing for you and PS is cheaper than cables. At least PS does add some nutrients.
Still, nutrients can be added without the PS altogether.
Thus we see no differences in growth without PS when the same nutrients are added back. Which mirrors the observations.
More reading on this topic and N's role:
Cookie Absent
Archaea Dominate the Ammonia-Oxidizing Community in the Rhizosphere of the Freshwater Macrophyte Littorella uniflora -- Herrmann et al. 74 (10): 3279 -- Applied and Environmental Microbiology
Regards,
Tom Barr