I finally did the whole substrate swap operation earlier today. I went with 25lbs. quick crete play sand and 50lbs. quick crete medium sand all washed. It took a while to remove all of the fish, gravel & decorations but the time was definitely worth it. I kind of like the new look with the sand substrate but I wish I could set up my tank to make it look much better. I wanted white sand but couldnt afford it at $16 per 30lbs. so I settled for the cheap sand and wish I could design the tank so it looks great. Anyone have ideas of a great setup for an arowana, black ghost knife fish, senegal bichir & fire eel?