[locojay]

I wouldn't turn off the filter at all. It's ok for the food to fall after a few seconds. This is how the cories will get some food. In my 20g I feed a couple small pinches on the the top for the top swimmers and then I hold a small pinch under water for a few seconds before releasing it so it sinks directly to the bottom. Turning off the filters probably won't hurt anything, but I don't think it will do any good to be worth the effort.

Your cories will probably like the sinking pellets but be carefull if you decide to use them. IME, I've had trouble with sinking pellets. The flakes will be eaten quickly but the pellets take a little bit longer. In my tank once the other fish figured out this was the last of the food left in the tank there was some shoving matches over the pellets. One of my cories lost some finnage to my dwarf gourami and eventually the dwarf gourami had to be moved to my 10g. If you use them just keep an eye on the tank until they're gone.

In the past I've used a net to pick up wafers that sat in the tank for too long. The vac won't do it, and if it's not time for a water change it's even more of a pain.