I have just recently noticed my Tang has a bulge in his tummy and is hiding away alot! More than normal, He is still feeding however but just isn't his normal zippy self! My ammonium levels are 0.5mg/l and have high nitrat levels of 30-35mg/l I do a water change every 2wks at 31.7G, I have a 73.98G aquarium my salinity isn't quite were I would like it at 1.024 currently so just on nuetral! How can I reduce these levels, as down here in NZ it's hard to find saltwater plants also, and I seem to be for ever changing water with no better results! Please give me alternative ideas/advice! I have only been in this hobby for 1 year now and am still learning! Sorry I have had my Tang for 6months now.