Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Plants need about 16 different elements to grow.
Some are already supplied: Hydrogen and Oxygen are things we do not worry about.
Some plants need in such large quantities that it is assumed that the tank needs them:
Nitrogen (fish food can supply some, but not enough for a high tech tank)
Phosphorus (fish food can supply some, but not enough for a high tech tank)
Some elements plants use in moderate amounts, but these are often present in tap water.
Calcium (if your GH is over about 3 German degrees of hardness your water probably contains enough Ca.)
Magnesium (if your GH is over about 3 German degrees of hardness your water probably contains enough Mg.)
Some elements plants use in very small amounts. Usually these are dosed together and called Trace or Micro nutrients. Iron is sort of marginal. Plants use enough iron that it is sometimes dosed in addition to a trace mineral blend.
Seachem offers several fertilizers already dissolved in water as well as slow release tablets. Other companies also sell fertilizers, wet and dry.
The Flourish line includes all the fertilizers and nutrients that plants need, bottled in separate bottles so you can customize the dosing.
I would get all of them, and dose as needed until you figure out the right ratios for your plants. Start with the label directions.
Flourish Nitrogen: If you are not feeding any livestock then plants can use quite a bit of N. Fairly generous dosing.
Flourish Phosphorus: If you are not feeding any livestock then plants can use a moderate amount of P. Be conservative. Low dosing.
Flourish Potassium: This is one that aquarium plants seem to use the most of. It is not in fish foods in high enough amounts, and not really in most tap water in high enough amounts.
Flourish Excel: Carbon source. Some plants do not like this, so start slow. Research the plants you are growing and see if anyone has had problems they can relate to Excel. Anacharis and Valisneria are 2 that do not like it.
Flourish Iron: This is the other nutrient that aquarium plants seem to use more of.
Flourish comprehensive: Trace minerals. There is a small amount of macros in this product, too. Not much.
Similar, dry fertilizers:
KNO3: for potassium and nitrogen.
KH2PO4: for phosphorus. Yes, it has K, but so little is dosed to get the right amount of P that the K does not really count.
K2SO4: Source of K, if you do not need to dose very much N.
CSM+B: Trace minerals. Includes some iron, but many people supplement with a bit more.
Chelated Iron: Good source of iron.
DIY yeast or pressurized CO2. Carbon in a form that all plants accept.