PPS pro/classic was developed by Edward over on APC:
http
/www.aquaticplantcentral.com/forumap...on-systems.html
It has been accused of just being PMDD with added PO4 among other things. People add the extra PO4 to cure the green spot algae associated with PPS. People with low K levels in their tap water have had problems with this method, so they need to add additional K.
Here is a summation from Clive at UKAPS:
"What puzzles me is that it's not clear what the major premise of the scheme actually is. The premise appears to be either that:
1. Excess nutrients cause algae.
2. Growth is controlled only by nutrients alone.
Both premises are erroneous. The first is easily discarded as there is sufficient empirical evidence to the contrary. The second also has been proven inaccurate but is much less understood.
Assume 2 tanks are setup with similar lighting, similar bioload, similar filtration and similar CO2. Assume the first is dosed PPS and the second EI. It cannot automatically be assumed that the EI dosed tank will have higher growth. First and foremost the light intensity will determine this. Say the light on both tanks is subdued to 1.5 WPG and both tanks are CO2 injected to 30 ppm. It's likely that both tanks are light limited. At 1.5 wpg and unlimited CO2, plants in both tanks will only uptake some rate "X ppm per day" of CO2. "X" will most likely be less than 30. If the tanks are similar as stated above both tanks will consume the same amount of CO2. Assume this number is 10 ppm per day. If we were to raise the CO2 injection rate in the EI tank to 40 ppm per day that tank would still only uptake 10 ppm because it's uptake, like the PPS tank is throttled by the low light. Addition of more CO2 (beyond required uptake level) has absolutely no effect on a tank that is light limited. Now the nutrients; because the 1.5 wpg throttles the CO2 uptake to 10ppm, the nutrient uptake is likewise throttled. Assume that at this level uptake demand of NO3 is 2 ppm per day. It is 2 ppm per day in both tanks regardless of what the actual NO3 concentration is in each tank. The light level ultimately determines the uptake demand of CO2 which in turn determines the uptake demand of the nutrients. The PPS philosophy says essentially "At this level you should only dose 2 ppm per day" whereas EI says "go for max dosing 2 is good but 4 is better". Say the EI tank were dosed at 4 ppm per day. It would make absolutely no difference to the growth rate in this case. High concentration by itself does not imply high uptake.
Herein lies the fundamental difference between these two schemes; The next day we can increase the light, say to 3 wpg. The PPS tank would now need an adjustment to it's dosing scheme. Higher light would drive higher CO2 uptake which then would drive a higher nutrient uptake. While the PPS tank has to tested and fiddled with the EI tank has no adjustment necessary. It is already being dosed at max uptake levels so it's adjustment is automatic.
Apart from the drudgery of testing, PPS has no automatic way of adjusting to increases in bioload either. If in 2 months your plants grow by 50% then there will be an increase in their uptake. It may not be exactly 50% but it will be significant so you'd have to make an adjustment there. Then, what happens after you prune? Biomass decreases and so does uptake - yet another adjustment. Again, with EI you are dosing the max so no adjustments are necessary. If there is lower demand there is lower uptake, if there is higher demand there is higher uptake. It just doesn't matter if your concentrations are higher than necessary. If you want to slow growth you now know where the throttle is - it's called the light switch."
I have never used PPS, so I can`t really comment on it from a personal point of view but, ultimately, I can`t really see the point of it over EI. EI in it`s own right can be adjusted and modified to suit the individual`s situation. EI gains its deserved reputation through making planted tanks easy for the beginner (my own experience), when so many planted tanks have failed before. PPS just seems to be an unnecessarily complicated (water testing, Blah!) variation on a simple, effective theme....EI.
Avoiding water changes seems to be all the rage at the moment, but I find they bring my tank to life with additional pearling and fish activity.
Dave.
