Airlock help

[psd123]

Put a Stout on yesterday afternoon and with 1kg of spray malt instead of sugar, this morning was bubbling away nicely, came back this afternoon and i had foam coming out of the airlock and no water left in it, should i be worried or just out some water back into the air lock and leave?

Cheers Paul

[edit1now]

Put a little hat of kitchen foil over the top of the airlock to keep the flies out. Put some more water in the airlock tomorrow or Tuesday when it should have all calmed down a bit.

[psd123]

Thanks for the reply will give it a go.

Cheers Paul