Originally Posted by Gregcoyote
I tend to agree, but even .1ppm phosphate is pleanty to grow algae. You need to export the algae, not just recycle its nutrients. A CUC just recycles most of the algae organics. Removing the algae from the system and throwing it away is how you use algae to strip organic nutrients in your water.
I agree wholeheartedly. But I don't think he will have any detectable phosphate. Not because it's not there but because all the algae eats it.
Removing the excess nutrients is what is required. Sadly, many people who have terrible amounts of algae do a water test and say "everything is 0" and think they don't have a nitrate/phosphate problem.
It's like an alcaholic saying the 100 bottles of rum in his house are all empty, so he doesn't have a drinking problem. But if a 40oz bottle is emptied every day, he has a problem.
A nitrate or phosphate level of 0 doesn't mean he doesn't have a problem. It simply means his algae are nitrate-aholics.