Smell it and look at it in the bag. If it smells bad don't use it. If it isn't moving, don't use it. If the water looks cloudy, don't use it.
You can culture live foods at home and have your own clean fresh supplies.
Daphnia, bloodworms (chironomid midge larvae) and blackworms will live on green water and or infusoria.
Brineshrimp will also live on green water but they need saltwater not freshwater.
The following link has information on culturing green water and other things for fish food.
STARTING OUT Make sure you have a pair, (1 male + 1 female). There is nothing worse than spending your hard-earned dollars buying a couple of fish to try and breed and ending up with a pair of fish of the same sex. Let's face it, to reproduce fish you need a male and a female. Two males won't do...
www.fishforums.net
---------------
You can feed the fish on raw or cooked prawn/ shrimp, fish and squid. Most pet shops sell frozen foods and marine mix is made from these 3 main ingredients and is a great food to use.
Other frozen foods include Mysis shrimp, Rotifers, Brineshrimp, Daphnia and bloodworms. You have some of these as live so that is fine.
---------------
You can use live insects and larvae for some fish. Small moths, flies, ants & ant eggs, mozzies & mozzie larvae, and aphids can all be used. If you find lots of them, freeze them and use later.