This got me thinking as to why it took such a long time to get my plants to take off in my second version of my tank. I mixed Wormcastings with black sand, added osmocote, dolomite and k2s04, capped it with eco. I figured this along with CO2 would get my plants off to a quick start, but it didn't. I didn't dose the water column consistently. I was travelling a lot for work and I thought the substrate would give me extra wiggle room. I think a good part of the problem started with inconsistent CO2, but even when adding enough CO2 to cause fish stress things weren't really happening. I was thinking the lighting was the problem (too little). That clearly was not the case, many were using less lighting than I but had good growth. Thinking about this a little more I think you have ultimately hit on part of the problem I was having, after CO2, I was effectively limiting other macro and micro nutrients because the plants I replanted did not have roots needed for uptake or storage. The plants really needed the water column fertilized badly in the beginning. Much like in a natural environment when a flood of nutrients from heavy rains or ice melts most likely results in plants uptake of most nutrients in these times from the water column, and likely store reserves in the roots for times when nutrients are diminished in the water.
Then the next thought was why does Diana Walstad and Amano have such good success not dosing the water column, and Tom has proven that Amanos water column fertilizing is extremely lean, the light not terrribly bright by PAR standards. Why is the growth so good? Better control of CO2, most definitely (for Amano), but another answer is the substrate, but not for what I initially thought. Its not necessarily the nutrients in the substrate in the beginning, its the fact the substate leaches nutrients into the water column thereby flooding the water column that is a reason for the initial success. Once the plants become established the soil then can and likely does become a source of nutrients for the plants. In our tanks this is secondary to CO2, but still important factor. In my setup Osmocote is slow release, the wormcastings were buried under ecocomplete, which is essentially inert in the beginning. In a newly setup tank this would not release a flood of nutrients into the water column, which is what plants need. This also explains why my crypts did much better than all my other plants. The crypts I planted had established roots, and could actually take advantage of the substrate, that stem and carpeting plants could not.
Maybe this is captain obvious stuff here, but my conclusion (which could be wrong, I'm not scientist and haven't tested anything) is that it makes no sense to limit nutrients in the water column, especially when first starting a tank with unrooted cuttings, when in fact plants really can only effectively take in nutrients from their leaves. The reason others can have success is due to the fact that the soil leaches what the plants need into the water column. Once plants are rooted and established the substrate actually become more of a beneficial nutrient source and allow one to be a little more flexible with the dosing. So if one doses the water column using EI and the substrate even if inert has a high CEC, it should be fine. Starting with a good substrate that is more inert (flourite, eco, turface etc) without dosing the water column along with ridiculously high lighting that some of us have used, gives little CO2 wiggle room and the lack of dosing in the water column further exacerbates the problem.
Slow but getting it, I think
