I had to take my purigen out of my 55g tank to medicate a month ago. I recharged it (bleach/water), soaked in prime water, and added back to tank 2 weeks ago. The purigen kept my nitrates really low when I first got it. Now, my nitrates are hitting 20 by the time I do a water change every week, and I noticed the purigen is not soaking up the tannins from the driftwood anymore. I put the driftwood in the tank to soften the water, so that's fine. But, I don't use carbon (only purigen), and I'm worried its no longer working. Is there any way to know if it is still working properly?