im only running 2inchs maybe 3 at the deepest and i two goby/pistol pairs and a single pistol in my 15tall. they do great work on keeping the sand sifted and clean.HTH
i second liveaquaria.com.......i have used them a bunch of times and been very pleased. i even have ordered and recieved coral when the temp was in the teens. everything survived.
i used it once....didnt go back to it. when you add the part B, it made my tank cloudy. i didnt like to see my tank cloudy, it was only cloudy for alittle while. didnt really notice any diference when using it. HTH