The leather isnt dead yet, but it looks like it is on its way out. :-(
For the record, I keep two urchins in my fowlr
system which has nitrates and they have been perfectly fine for years, I am NOT saying not to get the nitrates down though, thats necessary if you want to keep that anemone and any other corals alive.
The reading looks to me to be about 50 or so so yeah, get that down with water changes. I may be a bit confused, but are you running a canister filter? If so make sure you clean out any debris and gunk out of it as you can change all the water you want in the tank, if the canister isnt perfectly clean then you will forever have nitrate readings.
Hope that helps/.