Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Which leg of a 3-legged stool do you want to try living without?
Plants need about 16 elements to live.
If you short them any of these they will not live.
Hydrogen and Oxygen are OK.
Carbon is the element they use the next most of. Excel is a good source of carbon, if you do not want to go pressurized. I also use Excel for carbon. It was one of the first 'fertilizers' that I started dosing.
N, P and K are the next 3 elements plants use the most. These are the macros.
Fish food supplies N and P in reasonable amounts for a low tech tank. If the NO3 test is always showing there is some NO3 there (5-20 ppm) then you can assume there is a reasonable amount of P, also. If the NO3 test keeps dropping under 5 ppm, especially if it hits zero, then you need to dose N and P.
K is the element that is most often missing of these 3. When I was just getting into ferts this was one of the first I started dosing: Plants use a lot of it, and it is difficult to overdose. Just follow the label directions.
The secondary elements are the ones the plants use the next most of. Ca and Mg are usually supplied by tap water, unless it is softer than about 3 degrees. Then I would question if one or the other might be in short supply.
Iron is another element that plants use quite a bit of. Almost enough to call it a secondary element. Fish food usually does not contain enough iron. This is the other element I started dosing when I ran low tech but well stocked tanks.
Trace minerals- this is a long list of all the other elements that the plants use, but they use these in very small amounts. Fish food contains pretty much all of them, so if the NO3 test shows that fish food is supplying N in sufficient amounts, then you are probably also getting enough trace minerals from the fish food. Tap water has some of these, too.
So... if I had to minimize the fertilizers, here is the order in which I would do this:
K, Fe, C, and (if needed) GH booster for Ca and Mg, but only if the water is so soft as to suggest a possible deficiency.
2) If the NO3 test suggests the plants are using all the elements from the fish food, and need more, add:
N, P, traces.
There are 2 ways to do this:
1) Get a pre-mixed blend, an 'all in one' sort of fertilizer. Tablets that you put in the substrate are a good idea for this sort of dosing. They do not add C, but they are pretty good (read the label) for the other elements.
2) Get each element separately, then you blend them to make a mix that suits your tank. Dry ferts allow you to do this. Make a blend of macros in one bottle. Make a blend of traces and iron in another bottle. Excel in a 3rd bottle. Dosing would be alternating between macros and micros, and always Excel. 2 bottles per day. Or, you could dose a bit more when you do dose, but dose fewer days. Such as:
M = Macros, Excel
T = Micros, Excel
W = Skip
Th = Macros, Excel
F = Micros, Excel
S & Su, skip, and one of these is water change day.
3) Keep each fert separate, but use pump bottles for faster daily dosing.
Day 1 = N, P, K, Excel (4 bottles)
Day 2 = Traces, Iron, Excel (3 bottles)
Methods 2 & 3 will allow you to figure out which elements your plants are using, and customize the dosing for your tanks.
Method 1 allows you to do this to some extent: Under dose the tablets, and make up the difference with method 2 or 3, fine tuning it as needed.