THe API nitrate test I understand well. I already learned that the hard way myself years ago, lol! You have to shake bottle #2 well, the vial after adding #1, and then again after adding #2. I just shake everything madly now. I even shake the pH reagent before using it, lol! I really don't like the API stuff, have been looking to upgrade. What are you using?
With phosphate, here's what I have learned, and this is from scouring what all the ADA type serious plant people say. With the macro-nutrients, Co2, and light, everything has to be in the proper balance. Too much or too little of any of the above, and the plants can't utilize whatever is there in excess fast enough, and usually you get certain types of algae that can thrive specifically on that singe nutrient. SO in theory, you can boost an obscenely high amount of phosphorus as long as the plants also have enough nitrogen, potassium, light, and Co2 to be able to metabolize it quickly. To little of any of that and the plants can't work quickly enough to pull whatever the single high nutrient is out of the water. Not that I want to do anything like that. I have a phosphate test kit, it was literally 0. I got it up to almost 1ppm about 5 days ago, and it is steadily trailing back down. *****Of course, all this is in theory, I have no practical experience doing any of this, so I will post back if there is an algae bloom. Either way, I am not going to ever let the phosphorus get over 2ppm, trying to keep it around 1 for now, and supposedly the algae bloom from too much phosphate requires more than that.
I'll post up on the Co2 once I have it set up and going. Still trying to research the best parts. Again, I am not going high tech on this, I suppose it's Mid tech, lol! I just want to be able to control the Co2 levels just a little. And, it's mostly because of the damn red plants. I am almost obsessed with them. This red lotus is awesome. I always like the way they look, and I stumbled across a few little bulbs with just a few leaves a few weeks ago, and it is doing well. The leaves/pads are gorgeous. Then the red ludwigia, scarlet temple, and red crypt too.