I use both Aquapham 5-in-1 coral food and Marine Snow.
So far I do not have any algae bloom in my tank.
I also feed live plankton to my corals and clams daily.
I usually keep all of the foods (5-in1 coral, live plankton & marine snow) in the fridge after opening.
These food contains usually live bacteria that corals, clams etc need.
As brother mengyang_neo said, if the food smells bad, just throw it away. Not worth it of your main tank has so many problems after feeding spoilt coral food. A big bottle of Aquapharm 5-in-1 coral food only costs $13 in LFS in Pasir Ris.