This was interesting:
Plants experience oxidative stress upon exposure to heavy metals that leads to cellular damage. In addition, plants accumulate metal ions that disturb…
www.sciencedirect.com
A defense against toxicity. But we can still kill a plant with heavy metals even if it has defense mechanisms.
On nitrate:
Comparing the effects of high vs. low nitrate on the health, performance, and welfare of juvenile rainbow trout Oncorhynchus mykiss within water recirculating aquaculture systems
Their definition of low nitrate vs high nitrate is "below"
There are clearly negative effects from Nitrate.
But it's about concentration and exposure - toxicity will be based on concentration in that cell which is regulated by diffusion and relative concentrations in the water column -- not to mention the plants natural ability to moderate itself as seen in the toxicity paper.
You can ballpark your nitrate in the tank without tests. Keep a plant that goes red under limitation, use a floating plant, use your water report and calculate what you pour in, then add a bunch for decay, but what if you run purigen? Your plant mass is constantly changing and as a result, your test measurement from yesterday is now incorrect. How do you account for uptake of nutrients? What if you change your light intensity? What if you add more of another nutrient that was limited and you are able to uptake more nitrogen? What if you plant something? What if you change 90% water? What if you change 100% water with RO and use TDS as a measure? Why would we bother testing at the moment in time -- perhaps an APEX machine with constant monitoring of levels ... that would be very cool.
If you want to change no water, then you HAVE to moderate your dosage - otherwise you will kill absolutely everything.
EI is not about nutrients.
EI is about (and probably more):
1) High photosynthetic rates and healthy plants
2) Good maintenance - we are the caretakers
3) High O2 levels via gaseous exchange
4) High turnover and distribution of water
The ideology suggests that if we do all of the latter, then our fish are happy. I don't have enough experience to do this with discus and so on ... but maybe in the future.
Nitrate availability will drive photosynthetic rates - everything is made of out of nitrogenous bases (DNA, proteins - which form the foundations to cell division) ... so it makes a lot of sense (but I haven't looked at any papers on it .... yet).
If you take empirical evidence and consider those who utilize nitrate limitation ... they don't "limit" (but they don't need to pour it in either) phosphate or potassium for a reason - ATP and potassium's role in photosynthesis. Will phosphate and potassium cause issues at "toxic" levels ... of course ... even as they reach that threshold. And what the heck does limit mean? SURELY it is in excess of what the plant needs, otherwise the plant wouldn't be able to grow the next moment that the water passed its leaf.
Further, we cannot be throwing words like lean, excess, etc down without a relative point - no one will ever dose "properly" as it would require unique injectors at the plant to respond to the PRECISE mol required for every single chemical pathway.
The primary issue is language - the notion that "excess" nutrients did not cause algae was brought because people limited nutrients to the detriment of their plants. People get tired of explaining Liebig's Law, biochemical pathways, etc - AND people don't want to learn it either ... they just want an answer.
Everyone on this forum is trying to learn - as am I - and it might be worth us compiling documentation about each of the "methods" that are used with their pros and cons of each.
I think it is more important that we don't subscribe to a method - instead we learn the system.
In terms of the pinnatifida and
@Sammy Islam ... in theory, if it is toxicity - and it may be - then increasing calcium or cranking your light will help since calcium and micros use the same NSCC and light will increase the growth rate. OR - of course - reducing your micro dosage. I am interested to see if reducing micros exclusively helps your situation ... as that is what is most important.
EDIT: Just want to add the following -
https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.15283
If the plant has decided to switch to photorespiration due to inadequate carbon availability or ability to gain carbon (i.e. nitrogen driving carbon requirements too high or flow or whatever), then it will require more energy to do so and compensate. That said, it may need to sacrifice older growth. And pinholes may be it's way of doing so. Further, reducing light will reduce the demand of all nutrients -- and so if it is not toxicity, then a reduction in light or increase in CO2/nutrient distribution will work.
Or maybe not -
Effect of Carbon Dioxide on Photorespiration on JSTOR