This was super helpful I cannot begin to thank you enough for such a detailed and well explained answer
I do have two questions:
First, I do not have any livestock in the tank currently and will not for the next few weeks. So what type of routine would you suggest with just ferts and weekly water changes.
Second question is once I do stock the tank it will only be with RCS and Amano shrimp, given that they do not create much of a bio-load, what would I adjust from your original explanation?
With the absence of a heavy contribution from fauna, it actually makes it easier to do. The change throughout the week will be predominantly the result of plant uptake. With a high-tech tank (high light and pressurized CO2) and a heavy plant load, the maximum daily plant uptake of NO3 is about 3ppm. Initially, you will be nowhere near that.
So, decide how much N-P-K you want to consistently have in your tank (I target 25-3-25). Then, just before your water change, take a measurement to see how much remains at the end of the week, calculate how much will be lost with the water change, then add the necessary amount of NO3 and PO4 needed to hit the target after the water change, matching the amount of K to whatever you dose in NO3. Of course, algebraically, you can just take a reading after the water change, but reading it before the water change gives a little better picture of your tank activity.
There are two on-line calculators that can help you see this very clearly (after you spend some time playing with them). These are on Rotala Butterfly | Planted Aquarium Calculators & Information
. You use the “Nutrient Dosing Calculator” to determine your dosing regimen for the individual ferts and the “Fertilizer Accumulation” calculator to determine what the effect of adding your ferts will have on your tank longer term, given your water change levels.
Also, be aware that Flourish Nitrogen is only 50% NO3. So, when you dose, your initial tests will only reflect half of the actual NO3 reading in terms of total nitrogen added. The above calculator will show this.
I want to add one thing about water changes: when you calculate your water changes, be aware that your tank does not contain the amount of water that it is rated to contain. It is usually about 75-80% of the tank size. For example; my 29 gallon tank has only about 22 gallons in it. So, a 50% water change means that I change about 11 gallons. When using the calculators, try to put in the actual water volume for your tank.