I totally agree with Peter.
In my experience, Salvinia, Ceratopteris, Java-fern and -moss grow very well without adding micronutrients. A lack of these substances wouldn’t only cause reduced growth, but in most cases also pale, yellowish or necrotic leaves and so become evident. Perhaps the micronutrients get into the system through (live-)food and the use of peat, leaves etc. in sufficient amounts.
In our case, I don’t think that the limiting factor for plant growth is the amount of micronutrients, but the absence of Ca2+, Mg2+, HCO3– and the low pH-levels, that many plants are not able to cope with.
Apart from that, a far more general question is:
What is the best strategy to keep the water conditions as stable as possible? Is it to rely on regular water changes (e.g. every two to four weeks), or to rely on the (floating) plants as nutrient absorbers and avoid a water change as long as possible, as Patrick suggests.
For my part, I tend to changing 50% of the water regularly, because I think, that the water quality in an aquarium cannot be measured only by NO3– and other macronutrient-levels, but also includes other metabolic products (from plants and fishes) that accumulate in the water (e.g. phytochemicals, hormones etc.).
Furthermore, I think that the shock of a water change is far less significant, when a change is done in rather short intervals, than with more seldom changes. But that’s of course my personal opinion.
Greetings,
Martin