Originally Posted by mrdemin
Do plants get affected by the flow of water? I try to place them so that they are not disturbed by the current but find it very hard to do so (actually I redirect the current), especially the banana plants which sit on top of the gravel and almost never stay where I place them until they end up in some weird spot.
I also noticed almost everyone uses two plant supplements, is this necessary? Some people use those "tab" thingies that you stick into the gravel next to the plant. I have only the NutraFin plant gro but am not sure if that will be adequate. Should I see how it goes with this alone, or should I take extra precautions and just go for the other supplement as well?
According to the scientific data, the answer to your first question is yes. If your banana plants are shifting due to the current, you have too much current in that tank. However, some fish need currents (certain catfish literally must have good water flow) so you need to balance things with such fish. But aside from the fish species' specific need, the water flow in a well-planted aquarium should be minimal. Here's why.
The rate of water flow through the filter has an impact on the amount of oxygen drawn into the water, and carbon dioxide (CO2) expelled from the water in what we call the gaseous exchange. Surface disturbance speeds this up, as does higher flow filtration, airstones and bubble effects and powerheads. There are two detrimental issues to this: CO2 which is extremely important for plant growth is driven out of the water faster, and oxygen is brought into the water at levels beyond what is good for the plants. Plants have more difficulty assimilating nutrients when the oxygen level increases. But the more significant aspect is the CO2.
Submerged plants have difficulty obtaining enough CO2 in nature and in the aquarium; this fact is believed by many to be the reason for the inherently slow growth and low productivity of aquatic plants over terrestrial. Further, freshwater emerged plants have been shown to be more than four times more productive that submerged plants. The reason is because CO2 diffuses so slowly in water as opposed to air, and this limits the underwater plant's uptake of CO2 because the CO2 molecules don't contact the leaves quick enough to meet the plant's needs. Aquatic plants have to use enzymes to rapidly capture the CO2. When the CO2 levels in the water become depleted, these enzymes sit idle, so to speak, but the plant still has to provide energy to them. This results in a reduction in photosynthetic efficiency and therefore growth of the plant because energy is being wasted. Thus, any thing that removes CO2 in however small an amount will be detrimental to the plant's growth.
In a natural or low-tech system, the balance between the 17 nutrients (one of which is carbon) and light has to be there; so anything that may impact however slightly can become a critical factor in less success. The one thing we cannot "control" in this type of setup is the CO2, by which I mean that it is entirely dependent upon the fish and biological processes; with light we can control it, in intensity and duration, to balance, as we can with the other macro- and micro-nutrients through fertilization. Plants will photosynthesize up to the factor in least supply. Many have planted tanks that fail because the CO2 is the limiting factor, and algae will take over because it is better able to use carbonates for carbon than most (but not all) plants. The point here is that nothing should be allowed to negatively impact the CO2 in a natural planted aquarium.
The water flow is important for bringing nutrients to the leaves and roots, and keeping the leaves free of sediments. But there has to be a balance so as not to adversely affect the plants ability to assimilate nutrients including carbon from CO2.
With respect to your second issue, fertilizers: most natural systems have nutrients but not all of them or in sufficient quantity to provide the needs of the plants. The solution is a balanced complete fertilizer. Liquid works for all plants, whether substrate-rooted, rooted on wood/rock, or floating. In order to ensure the plant gets the required 15 nutrients aside from carbon and nitrogen that come from other sources in the aquarium, the fertilizer should be a comprehensive. These nutrients are required in specific proportions; plant growth problems can result from an excess or deficiency of several different nutrients. I only recommend what I've used, and this is Seachem's Flourish Comprehensive Supplement for the Planted Aquarium and the Kent Freshwater Supplement. I checked the website for info on Nutrafin and it wasn't very helpful. If you're using it and the plants are lush and green, it may be fine.
Substrate fertilization is obviously only effective for substrate-rooted plants. Echinodorus and crypts feed heavily through the roots, since most of the species are bog plants in their native habitat. Using a tab or stick next to the roots of the larger swords is certainly beneficial, in my experience amazingly so. I use Nutrafin's Plant-Gro sticks; they are less expensive than Flourish tabs, but the latter are also good.
As Money said, all this has to be in balance with your light and CO2 (the variable). There are very few plants indeed that will not grow well in a natural system with 1 watt of full spectrum light, adequate fish load, and supplemented nutrients.