I have removed my old substrate from my 125Gal, which was colored sand as a base and gravel on top. The substrate was approximately 3" to 3.5" deep. I removed about 2.5 (5gal) pails combination of sand and gravel. I have started replacing it with Black Diamond sandblasting Medium Sand. Questions: First, should I replace some of the original sand back as a bacterial bed (it's been in the pails for almost a week--it still damp). Second, should I go with only the Black Diamond or add Caribisea's African Cichlid Aragonite to create a Salt & Pepper look. My thought is my Community African Cichlids would benefit from the Aragonite and I like the look too. My tank has been running for several years (> 5yrs) with the old sand and gravel setup with no problems. As always any input is greatly appreciated & God Bless!