ceg4048;25668 said:
No, not only to lower pH. Peat is compose of decayed organic matter which means that it has organic carbon that can be consumed by the bacteria in the soil. The nitrifying bacteria need not only NH4 and oxygen, but carbon, phosphorous and other elements to grow. Later on the plants supply dissolved organic carbon to the bacteria but during tank startup this helps to feed and establish the bacteria colonies. So really any form of organic carbon placed in the substrate is a good idea, not just peat.
Cheers,
Adding to this, peat is not particular labile, thus will not be broken down readily.
So adding it will not cause anaerobic conditions in the sediment, unless you really "lard it on". Garden soil can and does, the forms of carbon available to bacteria are far easy to break down, thus bacterial decomposition rates will be much higher, generally a few orders of magnitude higher than with peat or leonardite etc
An issue for many is how to add the right amount, enough to supply the bacteria and plants with nutrients, but not so much as to cause very low O2 levels, low redox levels.
But think about it, plants live in these places naturally, submersed plants do best with relatively low OM in the sediment, 10% or less generally (see Barko et al on this topic for a reference). When we add CO2 etc and high light, the rates of growth are 10-20X what they are in natural systems.
So the plant roots are much better at dealing with low O2, lots of OM near their roots since they modify their environment by pumping O2 down into the sediments. Emergent plants are even better at it.
But you need to consider the influence of CO2 enrichment when making comparisons, that really amplifies the amounts of O2 in both the water column as well as the root zones.
So all the hogwash about cables, and larger grain sizes for circulation etc is poppy cock. Engineers need to get out, test the biological question with real plants in their models, not just pore sizes alone in static soils without measuring OM, bacterial rates of respiration, Redox and how plants modify the system.
Healthy growing plants are able to change and alter most systems to their liking.
The key is simply to keep them growing well.
Most of that tends to be centered around CO2 and good routine nutrient supplies.
However, texture does play a role for some plant species, Barko seemed to suggest this as well, but said most of the issue was organic matter(OM) %.
Too much= bad, too little = bad.
So a way around it is to mix it and encapsulate it in clay, much like ADA AS, but very unlike ADA PS.
This sort of tells you why ADA As is the main player in the effectiveness of ADA substrates, not ADA PS.........which goes along with observed results, as well as theory and research.........
I think there's 2 main ways to do this: DIY soil/mineralize it yourself, go collect it from a delta etc, use some composted material like Earthworm castings etc, let it mineralize some for a few weeks, or boil or bake it for a bit, mix it well with 2" sand and add about 3:1 or 2:1 in this sand base layer, then cap with 1-2" more of sand(2-3 mm is the ideal size). Or use something like ADA AS.
Now you can certainly add less soil/compost etc and say add only 1/4 of this suggestion, and still have decent results, but it will not last as long either.
All this also depends on water changes, good CO2, dosing etc.
You take better care of the water column, you get more out of the sediment.
Sediments tend toi be set and forget for many months or years.
Most of variation comes from the water column.
When I test sediments on plant growth rates as well as other researchers, we need a control, so often times they will grow the plants emergent/hydroponically etc or in flow through systems that remove everything from the water column except dissolved gases.
We tend to use a complete sediment/fert mix, then an inert one, then the sediments of interest in between.
This gives a good indication of how well they perform.
You can also look at tissue content for N, P, Fe, K+ etc if you wish as well(cost more, more labor/effect).
This way you can isolate the sediment's impact on plant growth.
However, in the real world, we add things to the water column or they are present in tanks, in natural systems etc.
So then you go back and see if you have any differences when you add those parameters into your test. Now you can say something about the effectiveness of a particular sediment of interest on plant growth.
But this information is still limited to the set up you used and tested(folk's tanks will be somewhere between). Also, you need to test each species of aquatic plant.
So about 300+ species/varieties.
Say 6-8 replicates X 300 species of plants, in a flow through system you could add them all, then a similar set up for a non limiting water column and one with and without CO2 enrichment at 30ppm.
So that's 7 reps x 300species x say 5 soil types x 4 bin treatments(No water dcolumn nutrients, CO2 or not, and water column nutrients CO2 or not).
Yikes.......42000 pots of plants.
One species: 140 pots.
So you could do that fairly easily and do accurate dry weights to get Relative Growth Rates.
So if you want to know why no one has done this, there's your answer
Give me a bunch of $, I can, but it'll take awhile.
Regards,
Tom Barr
