I have a 210 fowler with a porcupine puffer (very messy), angler, dwarf lion, dwarf angel, tomini tang, mag. foxface, and eel. I've always battled high nitrates (100 ppm, maybe more), but I was under the understanding that nitrates didn't really matter. Today, I was reading in another group and someone brought up nitrate poisoning. I looked into it a bit and there are differing opinions (of course!!). So, is this a real thing? Is it a cumulative thing? Are there warning signs? All my fish are active and eat like pigs. Now, my tank seems very healthy. My sump is COVERED with tiny feather dusters, my pod population is huge (they are all over the glass hours after I clean it), I can go 2 weeks without cleaning the glass (the reef tank is 2x a week), I have a few spots of cyano (PO4 is high as well) but no GHA or other algae (maybe the grazers eat it?) I do run a biopellet reactor that has been running since I tried lowering NO3 before and I am just using up the rest of the pellets. I tried NOPOX before, I tried a DIY algae reactor but the chaeto died. This is when I finally said that everyone is doing good, so why mess with it. The next step would be a sulfur denitrator but I read those stink (literally). So, are high nitrates in fact poison?