Plant fertilizers are made up of 4 major components:
d) Micros/Traces (iron, manganese, molybdenum, zinc, boron)
There are a few sources for these fertilizers:
a) fish waste products (costs nothing but more difficult to quantify)
b) buy them in liquid form at the pet store (most convenient but most expensive)
c) buy them in dry powdered form (economical and very effective but requires some labor)
If you buy bottled fertilizers from the pet store or online, just follow the manufacturer instructions. Make sure that you buy different bottles of fertilizers to encompass nitrates, potassium, phosphate, and micros. Your plant will not do well if one of these nutrients is lacking. You cannot buy a single bottle containing all these nutrients because they interact with each other and cannot be mixed beforehand.
PREPARING YOUR DRY (POWDERED) FERTILIZERS
The dry powdered form will cost much less, and all you need to do is add distilled water. You can buy dry fertilizers from many places including greenleafaquariums dot com, theplantedtank dot net buy and sell forums, amazon, and ebay. Buy a 1 gallon jug of distilled water from your local grocery store for $1. You will also need a digital scale which you can buy online or from walmart for $10. Find a scale that can toggle between different units (grams, milliliters, and pounds) with a maximum capacity of up to 10 pounds.
The dry powdered fertilizers that you need to buy are the following:
a) KNO3 (potassium nitrate which supplies nitrate and potassium)
b) KH2PO4 (potassium phosphate which supplies phosphate and potassium)
c) K2SO4 (potassium sulfate which supplies potassium)
d) CSM+B (micros)
Obtain a 1 liter plastic bottle. Use a measuring cup to fill the plastic bottle with 900 mL of tap water. Use a sharpie marker to indicate the water level at the 900 mL volume. Now throw away the tap water. Prepare a total of three 1 liter plastic bottles in the same manner, marking the 900 mL level on all 3 bottles. Make sure the bottle cap is not made of metal because it may interact with and degrade the fertilizers.
Bottle 1: This will contain your Nitrates
Add 117 grams of KNO3. Fill the bottle with distilled water to reach the 900 mL mark that you had previously drawn with a sharpie marker. Shake up all the bottles until all the powder is dissolved. Store this bottle in room temperature.
Bottle 2: This will contain your Phosphate and Potassium
Add 42 grams of KH2PO4 phosphaste. Add 48 grams of K2SO4 potassium. Fill the bottle with distilled water to reach the 900 mL mark. Shake up all the bottles until all the powder is dissolved. Store this bottle in room temperature.
Bottle 3: This will contain your Micros
Add 32 grams of CSM+B. Fill the bottle with distilled water to the 900 mL mark. Add 20 ml of glutaraldehyde (see carbon source section) to inhibit mold. Shake up all the bottles until all the powder is dissolved. Store this bottle in your refrigerator permanently to further inhibit mold.
This is the reason why we are only filling the bottles to 900 mL instead of 1000 mL. If you fill the bottles to 1000 mL, it will be much harder to shake and dissolve the contents. I have also learned that if you make the solutions more concentrated than the recommendations I provided above, then it becomes more difficult to dissolve the powder. It is best to use distilled water instead of tap water to prevent the trace elements in tap water from interacting with and degrading the fertilizers.
SCHEDULING FERTILIZER DELIVERY:
The dosing method I use is called Estimative Index dosing
which was originally developed and described by living legend Tom Barr. There are dozens of guides and calculators online that differ slightly from each other. The general rule of thumb is to provide the fertilizers on alternate days:
Day 1 - nitrate, phosphate, potassium (from bottles 1 and 2)
Day 2 - micros (from bottle 3)
Day 3 - nitrate, phosphate, potassium (from bottles 1 and 2)
Day 4 - micros (from bottle 3)
Day 5 - nitrate, phosphate, potassium (from bottles 1 and 2)
Day 6 - micros (from bottle 3)
Day 7 - 50% water change
Day 8 - Same as Day 1, repeat all over again.
Do not mix phosphate and micros on the same day because the interaction between those solutions in high concentrations will cause some fertilizer degradation. For this reason, the micros solution is administered by itself on specified days. The best time to deliver the fertilizers is the moment when the lights come on. Remember to also deliver the glutaraldehyde at the same moment.
The nitrates are in a separate bottle from the phosphate and potassium so that you can control the nitrate level and prevent fish toxicity. Nitrate concentration above 40 ppm in your tank is toxic to invertebrates (shrimp, crayfish) and some fish (e.g. neon tetras, dwarf cichlids, discus).
Measure your nitrate levels using a nitrate test kit and reduce your nitrate dosing accordingly to stay under 40 ppm
. You can buy nitrate test kits from you local pet store or amazon dot com, and this test kit is also included in the API freshwater master test kit. The amount of nitrate present in your aquarium will depend on fish quantity (fish indirectly produce nitrates), plant quantity (plants consume nitrates), light duration (more hours of light means more nitrate consumption), and how much nitrate fertilizer you are adding. Plants in general are not harmed by too much nitrates, even if you hit 200 ppm
nitrate which is more than 5 times the normal dose. You may even notice that plants look healthier and have larger leaves when nitrate concentration is very high.
The Day 7 water change is necessary to remove any toxins that have built up from fertilizers that were not completely consumed by plants. I schedule the Day 7 water change when the lights are off and the plants are not so actively consuming fertilizers. Specifically, I change the water a few hours before the lights come back on in Day 1, and I replenish the fertilizers the moment when lights come on.
For my 125 gallon tank, I use the following amounts on their respective days:
Bottle 1 (Nitrate) - 60 mL
Bottle 2 (Phophate and Potassium) - 60 mL
Bottle 3 (micros) - 60 mL
If you have a smaller tank, then use a proportionately smaller amount. For example:
For a 55 gallon tank, use the following amounts on their respective days:
Bottle 1 (Nitrate) - 30 mL
Bottle 2 (Phophate and Potassium) - 30 mL
Bottle 3 (micros) - 30 mL
For a 30 gallon tank, use the following amounts on their respective days:
Bottle 1 (Nitrate) - 15 mL
Bottle 2 (Phophate and Potassium) - 15 mL
Bottle 3 (micros) - 15 mL
For a 20 gallon tank, use the following amounts on their respective days:
Bottle 1 (Nitrate) - 10 mL
Bottle 2 (Phophate and Potassium) - 10 mL
Bottle 3 (micros) - 10 mL
Note that 1 teaspoon = 1 mL, and 1 tablespoon = 15 mL.
If you have a lot of red colored plants, it may be beneficial to increase your iron dosing. To do this, simply purchase DTPA Fe
(DTPA iron or ferrous DTPA) in powder form just like all the other dry fertilizers. Then add 47 grams of this DTPA Fe
powder into bottle 3 which is your CSM+B micros bottle. Do everything else the same way (no need to change the volume of solution that you pour into the tank).