I had some problems with the sump since it was not selled to the aqaurium and had a clown whent in the sump and i could not bring it and had to remove some of the mediato ry to get it so I think I hadd some prob with no2 ..... when I had notice that I hadd problems comeing I had stop the small marine tank and added the lifestiock in the tank....
I did not have any problems with live stock till know.... thge only problem had with the coral because it had change some conditions but knowe a differnt it cam better the it was since I have larger water volume and have a fuge with live rock so bactria can grow in the sump.
Valhmor