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[APD] The organics: Mulm, peat, lignite, soil
Folks have been asking what are mulm, peat and now lignite/leonardite are for and why add them.
Mulm- this is the stuff that settles on the bottom after you vacuum your substrate after you pour off the clear water. Another source is from your filter sponge. It's mainly plant leaf detrital matter or also from driftwood decay. Acting on this detritus are bacterial and fungi and a wide variety of smaller microscopic associated organisms in the upper aerobic regions.
This organic material is very labile, easy to breakdown and be reminerlaized for plant nutrients.
The main purpose for adding this if for an inoculate for seeding the new tank with live thriving organisms that are present in a healthy mature tank. It's much more than simply bacteria.
It has a great deal of surface area for the bacteria to live on, lots of the other associated organisms beside bacteria also but it also supplies the these organisms with a good food supply till the supply of detritus builds up enough in the new tank to supply these organism with a food source. The mulm also acts to protect the live culture when transferring. Mulm can be dried out and used in large amounts also when added the bottom layer of the substrate.
Peat- (I use ground peat moss, 2.39$ at Home Depot etc) peat is moderately non labile, it'll breakdown, but it'll only happen very slowly. It can act as the carbon food supply but this is slow. It acts to bind and chelate a number of of nutrients and when used in moderate amounts can enrich the substrate. It also adds some reduction in the new substrate which is lacking initially.
This moderate reductive nature allows better conditions that are similar to an established tank's substrate without waiting for the the tank to mature naturally. More Organic Matter(OM) will cause a mature substrate to have a greater reduction potential, Eh, and allow cations like Mn2+, Fe2+ to be released slowly but the trick is to have this reduction to occur slow and controlled. Too much labile organic matter wil cause the substrate to become too reductive for replanting and release all the cations to fast. You can add laterite, Flourite etc to buffer this OM reduction and this will work ar moderate loading of OM, but adding too much will be detrimental and cause too much reduction. The effect of the peat wears off after about 1-2 months and then your detrital OM cycle has already started and will maintain a good reduction level in the substrate.
The theory of heat cables goes back to this, not too much or too little reduction, but just the right amount(200-300mv). Instead of using thermal induced flow rates from above and asssuming the lower portions are reductive, peat/lignite uses OM and humics/fuvalic acids to accomplish this and the reduction, but it also adds OM that is different than the labile mulm that the cables would bring in/out.
It also adds more reductive material there from the start than the cables and the flow rate is slowed down, allowing better long term storage/sink of labile cations/nutrients. So in effect, the OM is better than the cables as it retains the nutrients better in terms of reduction and volume.
Cables do not add enough OM through the flow from above into the substrate and release most of it back into the water column. The same is true for RFUG's. If you add OM into the cable or RFUG set ups, you blow out most of the reductive nature that is optimal for the plant's roots. If there is no OM to start with, then there's little reduction ocurring and the conditions are not as optimal as they could be. Adding peat/lignite will help provide this.
Lignite/leonardite- is relatively new for planted tanks and is useful much in the same matter as peat, but is a little less labile, more concentrated and will last longer than peat alone. Some may find it a more workable material than peat over the long run. It will release the humics slower and allow a longer slower more controlled release of these reductive chemicals that will amplify the substrate's contribution and also will have some effects on the water column nutrient pool source(peat does this as well but has less effective life) and will bind some of these nutrients into the substrate but still keep them moderately labile.
You can add all three as each has a different purpose in terms of time, and mulm is always good to add to any tank to start the substrate off well. The only difference between a new and mature tank is the substrate and filter(but plants take care of that) so some amplification can be very useful for the substrate to get off to a good start.
Soil, I tend to keep seperate group as it has more macro nutrients and needs pre soaked for tanks in some cases depending on how you go about things. Pre soaking will ensure less issues in the future with algae as it removes the NH4/Urea present and bacteria oxidize the these into N03. NH4 generally is best added through fsh waste to the water column or with tiny amounts in healthy/low fish stocked planted tanks(even here folks can screw up if they get too wild). So soil is a good additive also if it's pre treated. You don't need a lot and the macro nutrients will be used rather fast in a CO2 enriched tank. It's pretty rich but the pre soak will make it's usage much less likely to cause you problems.
You can do the 3 week pre soak idea with any richer compost etc to reduce any algae inducement or perhaps boiling it will also oxidize it faster. Once oxidized from NH4=>NO3, the material is ready to add. You can also use KNO3/KH2PO4 and add peat if you want rich macro's in the substrate.
A slow release for NO3/PO4/K would be ideal for a macro base, the peat/lignite will help aid the micronutrients in that manner over time and may have some macro holding capacity also.
I think there might be something better and can hold more NPK than what's available, even a jobes stick allowed to NH4=>NO3 for a couple of weeks in some tank water in a container, then re dried out and added back to the tank's substrate would work I suppose. You could re enriched the stick with a strong solution of KNO3 and KH2PO4 and then dry it out and add to the tank.
Cheap, somewhat labor intensive, but anyone could do it.
Some might find it more to their liking than soil and frozen mud cubes being added to their substrate.
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