Tank Size:
58 Oceanic
OK on a 58 gallon tank I would do a 20 gallon water change now. As suggested use fresh carbon for 24 hours then replace it for 48 hours then replace that in 72 hours. Run a protien skimmer if you have one. If you can get your hands on a polyfilter then run that in your filter as well.
Get ready for another 20 gallon water change.
Use only RO/DI water, never tap water.
See if you can find a sponge to cover that powerhead, they do make them and sell them at LFS's.
Never purchase a white anemone or add a free white anemone to your tank, white is unhealthy for an anemone. Read the first post in this forum about purchasing a healthy anemone.
Thomas