anenome tank

Hi guys I’m a little stuck, and not sure what to do. My perms are all good my corals are all thriving but I have an issue with my anemones?? Just the nems which is weird no change to lighting either and they have been in the tank for about 4 months My BTA anemones seem to have gone a dark...

What’s the optimum flow rate for a nem tank? 10x, 20x, 30x, 40x, or even 50x? Thanks in advance!