Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Are there fish or other livestock in the tank? Fish food supplies most of the things plants need, but is lowest in K, Fe and Ca. (Potassium, Iron and Calcium)
Plants need about a dozen elements to live.
Some are already present (Hydrogen, Oxygen), but all the others need to be supplied.
Here is a brief rundown:
Carbon, in Excel. Most plants can use this just fine. A few plants do not like it. Some plants can get carbon from carbonates, but they only do this if there is no CO2 available.
Nitrogen, Phosphorus, Potassium:
Plants use more of these than the rest of the list that follows. Read the label on your root tabs to be sure they have these.
Some plants will take these from the water better, perhaps it would be a good idea to add some fertilizers to the water column.
Plants use these in moderate amounts, and usually the tap water has these. If the GH is over 3 German degrees of hardness, then I would assume the Ca and Mg are OK. If other solutions do not work, come back and test for Ca separately, then use a special formula to figure out how much Mg there is.
This is the 'trace mineral' that plants use the most of. You might need to add this separately, even if there is some in the products you are already using.
All the other minerals:
Plants use such small amounts these are all lumped together under the concept of trace or micros.
If the nitrates are zero pretty much all the time, but you are feeding fish or other livestock, then the plants are using all the nitrogen they can get and might need more.
I would dose the phosphates with the same thought as nitrogen: Fish food supplies both. Since the N is zero, then the plants may also be deficient in P.
K and Fe are the first two things I started dosing when my plants needed something in addition to fish food.