paludarium;34265 said:
Well, the authors did not use bare sand, but the sediment that would contain both nitrifying and denitrifying bacteria.
I thought you meant the bare sand without nutrients etc.
The plant increased denitrification by 30% or more.
So plants help NO3=> N2 gas, basically losing N. This is bad if you are trying to use NO3 as plant biomass/fertilizer( our tanks).
It also shows that the sediment, rather than a filter, can act strongly under good plant growth to nitrify NH4 via O2, and then the less aerobic parts, denitrify. In sediments without roots, the process never really gets going with NH4=> NO2=> NO2=> NO3 since it's an O2 intensive trasformation. The roots are adding lots of O2(this was measured here) and
enhance the bacteria, not just take up nutrients as NH4/NO3................
So what happens when you up root too much sediment? It's a bit like upsetting you filter too much.
If you purge your filter not too big of an issue in planted tanks, but if you purge too much sediment and the filter, you will have issues. Uprooting does other things like lower O2 overall oif you do too much.
Hard to say how much is too much, so anytime you uproot, make sure to do a large water change afterwards, keep the % of the bottom to say no more than 1/3 at a time perhaps 3-4days.
The link between roots, bacteria and plants and N seem pretty clear. Some suggest it's all about NH4 preferences etc. I highly doubt that. There are way too many things occurring in natural habitats and plants need many tools and forms of N and modify O2 levels to make it in wetland sediments.
They showed here that roots enhance nitrification/denitification and also sequester N(NH4/NO3). They increase the rates of uptake, transformations(NH4=> N2 gas export out of water), enhanced by working with bacteria.
Many of the wetland of the soils in CA are fairly N limited for this reason, so we have more P than N as far a critical ratio for plant growth of aquatic plants. Adding PO4 does little. Adding N does a lot.
In aquarist thinking, this shows that a healthy established root systems can and do dramatically increase the N load the tank can handle..meaning you can add a lot more NO3/NH4(fish or otherwise), and if you remove too much of this, you often end up with algae.
So this is maybe why some tanks use far more N than we might think and in our models, might use even more than 1-4ppm per day not so much in plant biomass, rather, bacterial biomass and transformation to N2 gas.
It also shows clearly that aquatic plants act as "pipes", pumping large amounts of O2 to the lower sediments. So why do we need heat cables or ADA power sand pumic to accomplish this when the roots do it and are far more active, natural and enhance bacteria better?
Instead we get folks carrying on about O2 levels down in the sediments that have NEVER once done a single wetland redox or O2 profile measurement.
They do not include the biological factor/s, the plants and bacteria.
Then they poo poo me and try to find things that contradict
The Reddy book in the other link is the best overall book with good pics on how things work. Note, this is a rather slow growing isoetiod plant , so most of our plants grow much faster and vigorous.
Regards,
Tom Barr
