Fertilizer

I would like members to consider the long term effect that the Macro and Micro ingredients present in fertilizers have on their fish. Be careful you may get your plants to grow but at the expense of your fish. This tank never had any Fertilizer added to it, it just relied on the fish population, as in the wild.

Although it's true that anything in the water gets into the fish through osmosis, most aquatic plant fertilizers, when properly used are safe for fish. As a matter of fact, I culture Red Russian Daphnia (among other things) as a live food source and daphnia are extremely sensitive to water quality. I use a small amount of aquatic fertilizer in daphnia bins to stimulate algae growth and it does not harm the daphnia.
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I feed the fish high quality live and commercial fish foods so there is very little fish waste. I find that if I don't supplement with a modest amount of aquatic plant fertilizer, the plants suffer and don't grow well at all.
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So all things in moderation.

In addition to what @AbbeysDad mentioned, I would point out that many aquarium plants are marsh/bog plants and obtain nutrients from the soil/substance they grow in. Those that are submersed also use the substrate as well as the water, but the degree to which the natural fish populations actually provides these nutrients is so far as I know not primary. For example, in the aquarium fish are the primary source of nitrogen which is the ammonia/ammonium occurring from fish respiration and more extensively decomposition of organics mainly fish excrement in the substrate. In the habitat, the organic load in the substrate is considerable, but due to several factors beyond fish excrement, primarily decaying leaves and other organics. The ratio of fish to water volume is vastly less than in most of our well-stocked aquaria.