Changing from Large Gravel to Sand?

The same thing happens in my 10 gallon tank. In my 5 gallon tank I have one betta and sand. I just bought some sand from home depot and washed it REALLY well (it took like 3 days of washing, draining, soaking, repeating.) I think you shouldn't worry about bacteria as long as you have the same plants/heater/filter because they hold bacteria. I would keep a little gravel in it because the gravel does hold bacteria. I think that sand is a lot cleaner than my gravel. Good Luck ;]