I have an Aqueon HOB Power Filter 50. There is quite a bit of grayish, pinkish stuff on my biological grid. I assume this is the "good bacteria" growing like it is supposed to. However, my nitrate levels have gone up recently. Ammonia and Nitrite both at 0. My question is can I or should I wash off the "stuff" in tank water, or should I just leave it alone and do water changes? Any advice is appreciated. I have an Aqueon 36g bowfront with 4 UDC's, 6 Zebra Danios, and 10 Golden Cloud Minnows. Not planted