I am familiar with PPS-Pro (Perpetual Preservation System) so I will describe it, however, both methods have commonalities.
PPS-Pro consists of a set dry salts in which you add water to them and dose a defined amount to your tank each day. I purchased Green Leaf Aquarium’s (GLA)
kit which comes with 4 macro fertilizers, 1 micro fertilizer, and 2 500 mL mixing containers. I also ordered a separate 500 mL mixing container. As per the instructions, you weigh out the macro fertilizers (oh, you need a scale that measures in grams) and the micro fertilizers and place them in their respective containers. To each you add 500 mL of distilled water and mix. It can take several hours to completely mix so the solutions will not be ready until the next day. For dosing, you add 1 mL of the macro solution for every 10 gallons of tank water each day. For micros it used to be the same dosage rate but a few years back it was scaled down to something like 0.4 mL per 10 gallons. That’s it! You perform water changes as normal.
I have deviated slightly from the above instructions. I mix and dose the nitrates (KNO3) separately because I found with the standard setup, the nitrates would be a lot higher than I prefer (40-80+). Thus, the extra container. I dose the nitrates 2-3x per week. Also, to combat green spot algae (GSA) I have tripled the amount of phosphate. I try to target 2-5 ppm phosphate.
With EI (Estimative Index) the dosage rate is much higher than PPS-Pro. The idea is to flood the system with fertilizers so that they are not the “weak link” in the Light-CO2-Fertilizer equation. I believe fertilizers are measured and dosed directly to the tank. Water changes are 50% or more per week to help “reset” the system.
I prefer PPS-Pro because it is easy to use and is inexpensive. I measure out and mix the dry salts about 1-2 times a year. I have a 20 gallon tank so I use about 2 mL of macro mix per day (a macro batch should last me 250 days). I bought the PPS-Pro kit from GLA in December 2013 and so far the only thing I’ve had to order was more micro mix (have not opened it yet). In two months it will be 4 years. Not bad for $25-35. Compare that against the cost of the bottled fertilizers and it is not even close.