I have a 55 gallon with 2 cichlids and 2 angels. recently i got rid of my gravel and replaced it with playground sand...which was washed till it ran clear. All was well, fish were unaffected i thought. We also found a home for our overgrown oscar two days later. Now the fish seem all sad...afraid of the light and hiding. Even the angels who usually are up at the top swimming gracefully back and forth, are huddled at the bottom. ideas?