Cheap and easy liquid coral food:
1 cup or small bottle/can of fresh oysters.
4 cups or bottles/cans of water.
1/4 teaspoon (NOT tablespoon) of Sodium Alginate (http://willpowder.com/sodiumAlginate.html). This will be about 1.2 ml
Blend for 5 minutes (this may overheat your blender).
Keep very cold (almost freezing), in a clear container so you can see if it separates.
If after a few days it separates, then put back into blender and add another 1/4 teaspoon and blend for a few seconds.
If it instead turns into a gel "block", then you put too much Sodium Alginate. Put back into blender and add another cup of water.
This makes about the same amount of food as a 32 ounce size of Oyster Feast ($65) for about $5.