If stuff looked unhealthy and/or dead, I'd be more worried - but everything *looks* fine, and has done for weeks.
You may have never started with uncured live rock before.
Unless you tell me you've been testing the whole time and this just showed up recently, that 100 ppm was just from die-off from when the rock was out of the water between the ocean and your tank...and is (or used to be) pretty normal for new rock in a new tank. (Seems like most get cured rock, or even dry rock these days....go figure.)
You sorta jumped the gun adding so much livestock so soon, so now it's best just to do away with the nitrates via a normal water change schedule. If you want to go back to whatever strategy was working before, I'd just do that after the numbers are all better.
If you think they guarantee no die-off you may want to contact them and see about this. (I have no idea one way or another....but not sure how they could ever make such a guarantee without being able to know what all has colonized their rock.)
You tell me you have 100ppm NO3. And that <.3 ppm ammonia = 0. OK.
I can tell you "what can cause it" or "what is normal".....but you have to tell me where it came from and if the tests are good as it's your tank and you are there.
100 ppm in just two months...even with too much livestock would mean a lot of over feeding and otherwise-terrible husbandry....way more than any normal overfeeding situation. Feels like reaching...
But test again and see if the number is going up or down.
My guess is that it's trickling down due to denitrification within the live rock and sand, but barely due to the amount of nitrate being added by the fish.
It's also possible that the fish are exceeding the (current, possibly under-developed) denitrification capacity of the rock/sand and that ppm is static or going up.
In my book 100 ppm is really, really high nitrates....the only time it would be acceptable is after curing/cycling and before livestock are added. Some folks wouldn't even let it get that high and would do some water changes during cycling. Once the cycle is done, the water is corrected and only then is when livestock goes in.
Another angle to consider (assuming still that the 100 ppm is accurate) is that 100% of that nitrate started out as ammonia....so what livestock went through how much ammonia exposure is an open question.
If you have to ask...yes!
I was serious about Paul...the recent thread...and his book. Worth researching for anyone serious about keeping fish.
Seems like too large a drop for just the scope of our conversation...but if you can take readings for a few days in a row, hopefully a nice trend will reveal itself. Perhaps it'll resolve itself at the rate you're seeing now.
Nitrates don't seem to be directly toxic...supposedly in excessive quantities nitrates can start replacing oxygen in some biological processes...probably not for the better....but I don't know the depth of what that really means. I did only a little reading, but seems that freshwater critters are more sensitive than saltwater....but the extent of the sensitivity or if there is a toxic level weren't clear.
I can't say impossible, but typically in a tank full of clean-up-crew a corpse of anything doesn't last long enough to look at. When something dies in the middle of the night and you miss it - you just have to wonder what happened to that critter, cuz by morning it is G O N E. So nothing left to rot. I don't think they could amount to 100 ppm when just considered as food, but I could be wrong.
... but your point is well taken. As for the water movement and surface agitation, I have a Jebao 25 in "Else" mode that broils the surface of the water, so I think the gas exchange from that should be good. I also have a good skimmer, which I believe also helps with this. Nevertheless, at mcarroll's suggestion, I will add another powerhead to induce a bit more turbulence.
