The emperor angelfish is acting really stressed out since this week, his coloration isn't great and he's making these short, dashes. Sometimes crashing into something. Amonia test indicates nothing, NO2 nothing, NO3 is still too high. Salinity is 32. Frequent water changes isn't really helping. I should probably get more test kits, maybe I'm messing up some other value.
I did notice the skimmer often stopped producing foam, because the sump water level often drops below it's working height. The only way to counter it is to top up the water higher then it's supposed to be in the sump. Even then it's not doing much lately and it has no options to tweak it. It's this old, square Tunze thing. So I just now got another one, second hand: Theiling E Cone 2000, it seems to works great. Producing foam and then some. If it will really help is another question ..
I don't know, not sure what to do here, but the emperor sure doesn't look good. Most of the other fish seem fine, although the emperor's behavior seems to be stressing out the yellow tang. Both of them used to swim around, now they are both just hiding in a cave.