I’ve been experimenting with coir for the past year and like some things about it. I like the way it looks, but I don’t like the fact that it falls apart (get’s fluffy and lose) over a few months. The tight mat softens and settles into the tank and over the months begins to break apart easily. It still stays down in the bottom of the tank. It does not float after it breaks up. That is good. But I don’t know how it will act with this new method of precharging and roots growing into the coir. In the past I weighed down plants with rocks on top of it, or poked holes in it to pull roots through, but the roots didn’t grow into the coir quickly, like they are doing with the precharged coir. So maybe the roots will help hold it together.
It is easy to pull plants out of the coir once their roots have dug in. It feels like pulling a weed out of heavy mulch. The roots release easily, and I can weigh the plant down in a different place, or in a new sheet a coir until it’s roots grow back in again. That is good. Because unless the coir behaves differently by precharging, it will probably need to be replaced in about six months, or sooner.
It may be possible to leave old coir in the tank and just lay another precharged (or not) sheet down on top of it if I see no molds and the old coir doesn’t smell bad. I have seen some whitish moldy looking stuff on three month old coir. But it looked no different than the mold/bacteria that can grow on tanks with other substrates, and even glass bottom tanks. It does hold nitrifying bacteria well, but I keep a UV light on the tank to keep any other odd bacteria or fungus under some control.
UPDATE: The precharged coir is much stiffer, and is not breaking apart, although it remains pliable. I have heard that dolomite is used in cement, so somehow the precharging tightened up the coir. This is unexpected, but good. It means I will be able to keep the coir in the tank longer without it falling apart. I wonder how long it will stay together? Time will tell.
I have added 1 cup each of the following into about 75 gallons of water in a stock tank. It takes an hour or two of intermittent stirring to dissolve. The coir mat will go into the mixture for a few days to pre-charge with fertilizers. The coir soaks for about 7 days. It is taken out and rinsed thoroughly before placing in the tank.
KCl: Muriate of Potash
MgSO4: Epsom Salts
I will add fully chelated iron, FeEDHHA, phosphorus and possibly other trace like MnSO4, directly to the aquariums after water changes.
What nutrients will be taken up by the substrate?
Now here is the real question. This will also answer your question if it possible to fertilize in large doses based on the belief that the substrate will take up the nutrients.
When we talk about the soil releasing and taking up nutrients we are referencing the soil CEC (cation exchange capacity) and AEC( anion exchange capacity). The AEC soil capacity is mostly covered by hydroxyls but under acid soil pH it can be a source of H2PO4-
Thus the main interaction relates to CEC, exchanging Ca(2+) Na+ K+ for H+ (mostly). This is all fine for cations (have a positive charge). However our fertilizer also have NO3- , PO4(3-) which will not interact with CEC but will remain in the water column until consumed.