At the end of the day you end up tailoring your dosing based on how your tank runs, how the plants look, algae levels and what water testing is showing. I used EI as a starting point and scaled back until plants looked like they weren't growing as well, then upped a mild amount. The aim then is to try and keep that level ongoing. Things change though, for instance you do some uprooting and replanting and nutrient requirements may change as new plants adapt etc. There are a few variables with fert dosing and I don't agree with just dose EI or PPS and everything will be fine... it is very tank dependent.
All coming around to say, you learn by feel. Your tank is unique and you'll get the hang of it.
Don't be discouraged by me highlighting that there's a little complexity to fert dosing. PPS Pro is a good method, so is EI. Out of the the two I prefer EI for high light CO2 tanks and I do a version of PPS Pro in my low light low tech. I don't call it EI or PPS Pro, instead it's a mish-mash of methods that suit the unique conditions I find in my tanks. All of this came from watching plants/algae/water-testing over time in these setups and some trial and error.
Essentially all you need to know is that you must supply nutrients in non limiting amounts, or mild excess so that plant growth is never limited by nutrient levels. Once you get that right you can move on to light and CO2 as factors in plant health.
Test your nitrate level just before a scheduled water change. This will give you a ballpark idea of nitrate accumulation and help you figure out how much N to add as fertilizer, if any at all. Testing phosphate and iron is also very handy but these are usually extracurricular. For low tech I like nitrate at <15ppm. In a high light CO2 heavily planted setup you can push N as high as 30ppm.
Here are the nutrient ranges for EI:
NO3 range 10-30 ppm
K+ range 10-30 ppm
PO4 range 1.0-2.0 ppm
Fe 0.2-0.5ppm or higher
Those levels are for high light CO2, smaller amounts can be dosed for low light no CO2. Once you know the maximum nutrient concentrations that super powered high tech tanks can absorb, you can guesstimate where your tank fits in to that equation. If think it's about half as hungry as a high tech, dose half of the maximum range for that nutrient and watch the tank/plants closely for any changes. If the plants still look hungry add some more etc. If you find that your nitrates climb over the week (test for this) you may add no nitrate at all. Your eyeballs are the best judge of plant and tank health but testing gives you another insight into what's going on 'behind the scenes'.
Last edited by Darkblade48; 01-20-2016 at 01:35 AM.
Reason: Please use the edit function for back to back posts