45 Plant Survival: Other Information
Description
This article is from the Aquaria: Plants FAQ, by multiple authors.
45 Plant Survival: Other Information
Some plants can concentrate carbon, potassium, nitrogen, phosphorus,
iron or the lesser trace elements and store it for later use. This
means that plants may do well for a while, using stored nutrients, and
then mysteriously wither if they can't replenish their supply. This
also means that some plants may "out-compete" others for required
nutrients, preventing the other plants from doing well.
Regular water changes are an important part of keeping a planted
aquarium healthy since many of the nutrients and trace elements are in
tap water. Changing 25 percent every two weeks is recommended.
The substrate can play a major role in the availability of nutrients.
Nutrients can be put in the substrate when an aquarium is setup by
mixing laterite (tropical clay), potting soil, peat moss or commercial
equivalents into the lower layer of gravel. These additives will
release some necessary elements and provide chelating sites so that
the correct ionic states are maintained. However, if nutrients aren't
replaced, the substrate will eventually be exhausted and the plants
will begin to do poorly.
If laterite or peat is used in the substrate and a very slow flow of
water can be forced through the substrate, water-born nutrients will
be chelated by the laterite or peat. This will provide a continuous
source of nutrients in the substrate. Substrate heating coils are
recommended for this since they can provide slow convection currents.
They are expensive, however.
The following table is based on data from the Feb, 1988 "Today's
Aquarium, the International Magazine of the Optimum Aquarium",
("Aquarium Heute" in German), published by Aquadocumenta Verlag GmbH.
Average nutrient content of plants and aquarium water
+-----------------------------------------------------------------+ | Symbol Nutrient Plant Water Absorbed as Concen| | mg/kg mg/l Factor| +-----------------------------------------------------------------+ | O Oxygen 48,000 880,000 H2O 0.02 | | Abundantly available in the water | | | | C Carbon 36,000 Varies CO2(HCO3-) 1000 | | Absent if no CO2 injection | | | | H Hydrogen 6,000 110,000 H2O 0.02 | | Abundantly available in the water | | | | K Potassium 3,600 5 K+ 1000 | | Sufficient with good feeding, otherwise fertilizing | | | | N Nitrogen 3,200 5 NH4+/NO3- 1000 | | Too much nitrate with good fish feeding | | | | S Sulphur 660 15 SO4-- 50 | | Source: fish food and mains water | | | | Ca Calcium 650 90 Ca++ 10 | | Absent in soft water | | | | P Phosphorus 460 0.1 HPO4--/H2PO4- 1000 | | Too many phosphates with good fish feeding | | | | Mg Magnesium 210 18 Mg++ 10 | | Absent in soft water | | | | Fe Iron 15 0 Fe++/Fe+++ 1000 | | Absent under good light, unless fertilized | | | | Other Trace elements 10 0 Ions 1000 | | Sufficient with good feeding, otherwise fertilizer | +-----------------------------------------------------------------+
Notes: "mg/kg" and "mg/l" are roughly parts per million or "ppm"
"Concen Factor" is how much plants can store beyond their needs for
growth, i.e., plants can store 1000 times more iron than they need.
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