ML> back to the substrate/gravel... you should have at least 2 to 2.5
ML> inches of substrate... that's about 10 pounds for each 150 square 
ML> inches of tank surface...

 MB> Whats substrate? 

that stuff you put on the bottom of the tank ;)

 MB> I usually use just gravel, or is substrate for salt water setups?

nope 8)

)\/(ark