Fertilization Methods

There are three fertilization techniques. The most novice technique is to buy a bottle of micronutrients and a bottle of macronutrients from your local pet shop and follow the dosing instructions on the bottle. This is not the best of ways since the concentration of each nutrient in the bottles is not known so quantity of each nutrient in the aquarium cannot be controlled very accurately if not at all. It is a very blur estimate that sooner or later will show it was a bad choice in the first place unless the plants in the aquarium are of minimum nutrient requirements, large weekly water changes are made and the light source is not too strong or on for a long time. Therefore if you wish to go ahead with this technique it is better to have plants with low nutrient requirement (slow growers) which will ensure that the nutrients in the water column are adequate for such plants. Weekly water changes should be carried out to ensure that there is not built up of nutrients which will cause an algae burst but also that the lights are kept on for a bout 6 hours per day and have a intensity of approximately 0.2 – 0.4 watts per litter.

The second technique is a lot more accurate but also more expensive. Seachem and EasyLife are two excellent product lines that have all the required nutrients in bottle ready to be dosed separately. Potassium, Nitrogen, Phosphate, Iron, Trace Elements and liquid CO2 are their major products and will cover the nutrient needs of almost all plant types. A dosing regimen suggested by Seachem is displayed below:

Seachem Planted Aquarium Dosing Chart

It won’t always be necessary to dose your aquarium with each of the products in the Flourish line, but as an example, we have developed one possible dosing regimen using all of our plant products. This is by no means the only way to dose your aquarium; it is merely a suggestion. Your dosing regimen will depend greatly on a variety of factors, including lighting, initial water quality, how heavily stocked your aquarium is, substrate selection, and types of plants; so don’t be surprised if getting the results you want takes a little experimentation.
Day of the Week Product Dose
Day 1
Flourish 1 cap per 60 US gallons (240 L)
Flourish Excel 1 cap (5 ml) per 10 US gallons (40 L)
Flourish Iron 1 cap (5 ml) per 50 US gallons (200 L)
Flourish Phosphorus 1/2 cap per 40 US gallons (160L)
Flourish Nitrogen 1/2 cap per 40 US gallons (160 L)
Day 2
Flourish Trace 1 cap (5 ml) per 20 US gallons (80 L)
Flourish Excel 1 cap (5 ml) per 50 US gallons (200 L)
Flourish Iron 1 cap (5 ml) per 50 US gallons (200 L)
Day 3
Flourish Potassium 1 cap (5 ml) per 30 US gallons (120 L)
Flourish Excel 1 cap (5 ml) per 50 US gallons (200 L)
Flourish Iron 1 cap (5 ml) per 50 US gallons (200 L)
Day 4
Flourish Trace 1 cap (5 ml) per 20 US gallons (80 L)
Flourish Excel 1 cap (5 ml) per 50 US gallons (200 L)
Flourish Iron 1 cap (5 ml) per 50 US gallons (200 L)
Flourish Phosphorus 1/2 cap per 40 US gallons (160L)
Flourish Nitrogen 1/2 cap per 40 US gallons (160 L)Day 4
Day 5
Flourish Potassium 1 cap (5 ml) per 30 US gallons (120 L)
Flourish Excel 1 cap (5 ml) per 50 US gallons (200 L)
Flourish Iron 1 cap (5 ml) per 50 US gallons (200 L)
Day 6
Flourish 1 cap per 60 US gallons (240 L)
Flourish Excel 1 cap (5 ml) per 50 US gallons (40 L)
Flourish Iron 1 cap (5 ml) per 50 US gallons (200 L)Day 6
Day 7
Prime Use 1 ml per 10 US gallons (40 L) to dechlorinate water
Alkaline Buffer Use as necessary to establish desired pH and KH
Acid Buffer Use with Alkaline Buffer as necessary to establish desired pH
Equilibrium Use as necessary to establish desired GH

Therefore to follow the above regimen, one must be dedicated enough to dose the aquarium everyday but also to make observations that will indicate the need to modify the dosage or regimen.

The third technique is called the Estimative Index and it has been developed by many aquarium hobbyists over the years. This is basically based on the same principal as the above technique with the only difference that the nutrients like Potassium, Nitrate etc are dosed from solutions that are prepared from dry fertilizers and water. Because the preparation of these solutions is a rough estimate of the nutrient concentrations in each solution, the dosing is made is such a way to ensure that a high quantity of these nutrients is maintained in the aquarium. By the end of each week a 50% water change is made and all the nutrient levels in the tank are essential reset thus eliminating any chance of very high or very low nutrient levels which will cause any unwanted results like iron poisoning or algae outbursts. Before continuing to a deeper explanation of the Estimative Index a quick summary will make things clearer. Specific dry fertilizers are bought from flower shops. These fertilizers are then dissolved in certain concentrations with water so as to be able to estimate the amount of each nutrient being added to the aquarium per mL of each solution so as to establish the wanted levels per nutrient.

What are our target levels?
K 5-30 ppm
N 5 ppm

Where are the above nutrients found?
KNO3
K2SO4

Now using Chuck’s Planted Aquarium Calculator the solution to be mixed can be calculated. How many grams of dry fertilizer are required in X ml of water in order to produce a solution where each ml added in the aquarium will increase the targeted nutrient by Y ppm up to the desired level. Take a look at the following example:

We would like to have Nitrate levels of 5 ppm in a 40 gallon tank. Using Chuck’s Planted Aquarium Calculator we can see that when we set the “Tank Size” to 40 gallons and the “Amount of water to mix with” to 250 ml then by adding 61.5 g of KNO3 we get 1 ppm of Nitrate per 1 ml of the solution. Therefore by adding 5 ml of the solution we establish 5 ppm of Nitrate in our 40 gallon tank. The same can be carried out for the rest of the nutrients but make sure that when calculating Potassium (K) you take into consideration the Potassium added by KNO3. It is thus suggested to add first the KNO3 solution, calculate how much K has been added by that solution and top up the tank to the desired level of Potassium by adding K2SO4 solution.