freshwater aqaurium setup

Question
we are doing a school project and we have to do some research.i have to find out if it is a good thing to put sand on the bottom and gravel on top of the sand.Is that a good idea???

Answer
Some people so put sand in there tanks.  Some put soil (for planted tanks).  Sand can cause a number of problems.  You have to be careful what fish you put in that tank. Even with gravel on top, you will have problems with the sand getting stirred up and having cloudy water.  Some sand can also contain metals that will alter your water chemistry.  Plus, you can't use an under gravel filter.  I personally don't recommend it.  If you want the look of sand without all the hassle, you can get river sand that is coarser and heavier, but again, you have to be careful what kind of fish you put in.  The sand can be sharp and any fish that digs or has barbles on it's face will have problems.