Thanks for the comments. They are oak leaves I bagged a couple of years ago. I have enough to swap them out when they get mushy and start to break up. I like the effect of the light through them. I'm not worried about leaching as I am running peat in the filter. I'm not sure what to expect for nitrates in this tank with the peat filter and low lighting. I'm running about 6w of led lighting for about 4 hours a day. I'm really into the low light almost spot lighting look - the antibox of light. -Andy