Most important for plants is Co2... and you need know both your pH and KH to know that, counting bubbles per second is useless..... a Co2 level of 25 mg/l is best for optimal plant growth (which keeps algae down).... forget about NO3 or other fert test kits.... go search for Tom Barr aka plantbrain's article on the "Estimative Index" in the Aquatic FAQ section (thread posted by juggler) for a no-brainer method for regular dosing that doesn't require testing. The other articles in that section on fertilisation are also useful.
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