info for me growing

Do I have to feed my cultures as they are growing?

• Bacteria, mold and yeast are like us, they all need some sort of food source. Agar is the standard growth medium for the culturing of bacteria, mold or yeast. Agar is extracted from type of red algae and is a polysaccharide (a type of carbohydrate) which is an ideal growth medium for these microorganisms. Additional food or nutrients can be added to the agar to make your cultures grow more successfully. When agar is mixed up it resembles Jell-O. It is available usually in a powder form that is mixed with water and nutrients to make a gel that you can use to grow microorganisms. It also can come premixed in gel form.
  Using agar alone will support microorganism growth. Adding additional nutrient (an additional type of food) will make your culture grow more successfully. Microorganisms are similar to you and I, we all like some types foods and not other types.
• You can add a small amount of chicken, beef or vegetable broth to your agar mix. Note: Be aware that salt and preservatives will kill or slow the growth of microorganisms. Broths labeled "organic" and/or "low sodium" are the best to use because they most often have the lowest amount of salt and preservatives. Add only add a small amount of broth, about 5 ml (just under a teaspoon) of each 250 ml (just under one cup) of mixed agar. Add any broth to the agar / water mixture before you boil the agar.  This will sterilize the broth when you sterilize the agar / water mixture.  You can also add small amounts of sugar instead of the broth if you want to promote yeast growth.   Again always add any nutrients to your mixture before you boil it.

from http://www.scienceenterprises.com/growingbacteria.aspx