Plants need over a dozen elements to live. Some are already supplied (like hydrogen and oxygen).
Some need to be added to the tank, but are added in ways you do not think of as fertilizer, such as fish food and water changes (depends on what is in the water).
Plants use the most of:
hydrogen (H), oxygen (O), carbon (C).
The only one to worry about is carbon. In a low tech tank carbon may be added simply by fish respiration and other natural ways. You can supplement carbon with a liquid carbon product like Seachem Excel or similar product. You can add CO2 via a yeast and sugar system.
Plants use the next most of certain elements that we refer to as macros.
Nitrogen (N) enters the tank in fish food. Test the NO3. If it stays so high you need to do water changes then do not dose N. If it stays too low, then add enough of KNO3 or other nitrogen fertilizer so the test reads between 5-10ppm. I do not know what is included in the product you are using, or the suggested dosing. There are some forms of nitrogen fertilizer that will not read accurately when you use a test for NO3.
Phosphorus (P, fertilizer form is usually PO4) enters the tank in fish food. You can use the NO3 test. If the NO3 from fish food is OK, then you can assume the PO4 is, too. If the NO3 from fish food is not enough, then you should dose P, also. You will have to figure out how much and how often.
Potassium (K) is in short supply in fish food. Even if the N and P are OK, dose K.
Plants use the next most of certain elements that are referred to in agriculture as secondary nutrients.
Calcium (Ca) and Magnesium (Mg) are tested with the GH test. If the GH is OK for the fish, then it is probably OK for the plants, but a level of at least 3 German degrees of hardness is good. If your tap water does not provide this, then add GH booster with each water change. If the plants and fish use it up through the week, then you can dose more with either macros or micros.
Sulfur is another secondary nutrient, but I have not heard of sulfur deficiency in aquariums.
Plants use the least of the minerals we refer to as micros or traces. These are generally lumped together. The only 1 that needs attention is iron. Fish food is a reasonable source of most traces, but not iron. Plants use a lot of iron, and iron often gets locked up in a way that plants cannot use it. When you add iron to the aquarium make sure it is in a chelated form.
Some trace mineral fertilizers do not have very much iron. To get enough iron you would be overdosing the other minerals. This could become toxic. Do some research and figure out if you need to add some additional iron to your micros.
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Once you figure out which fertilizers your tank needs, and how much, it is a very good way to dose if you alternate the ferts in 2 groups:
Days 1, 3, 5: Macros: N, P, K
Days 2, 4, 6: Micros: all the traces, extra Fe if needed, GH booster if needed.
Day 7: Water change: GH booster if needed.
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I just took a look at the Easy Life web site.
They sure have some old ideas, and a mixed up chemistry.
