Let's get the stats on your system. Answer the following:
What are the dims of your screen, Length and Width?
How many GPH are you pumping across it? Is the answer the actual measured flow, or calculated based on a pump head loss chart?
How many hours/day are you lighting the screen? Single photoperiod, or do you split it up throughout the day?
How many days do you let the screen grow between cleaning?
Now about your tank:
BEFORE you added the scrubber, this is what you said was happening:
[quote[Currently the main reason for using an ATS is to help reduce my nitrates, hopefully to an undetectable level. Because the rate at which nitrates are produced in my tank is clearly much higher than my weekly water changes can remove it. It resulted in a nitrate level of about 150-200 mg/L. After a week of daily water change, I ended up with about 50mg/L nitrates. Right now, nitrates are reaching 100mg/L again, even though algae is growing like mad in my ATS. I'm just crossing my fingers and hoping that this week's growth can bring the nitrates down a good amount.[/quote]
So let me see if I have this correct: After PWC, 50 ppm (mg/L). One week later, 150-200 ppm. That's a 100ppm increase in one week, or possibly as much as 150ppm increase
AFTER scrubber, you have having this:
Nitrates at ~25mg/L right after my weekly water change, and tested again before the following week's water change, it raised to ~50-70mg/L.So if I am understanding this right, you have roughly a 50 ppm increase in one weekOn tuesday after water change, it was 25mg/L. Today, it reads 70-80mg/L
That's assuming the same % of PWC each week.
I get your frustration, you want it not to rise at all. But you have to look at the positive side of this - your tank is much healthier going from 25-75ppm instead of 50-150 (or 200).
But before I jump to a conclusion, answer the questions in the first part of the post, and then correct me if I wrong in any of my assumptions or interpretations of your posts