I tested for malic acid tonight. We're still above 300 ml, so no rush with moving the wine from our carboy to the barrel. You want to make sure you prepare your barrel, though, too. Making sure there are no leaks or issues with the bungs before you put your wine into it. So tonight I filled it with hot water, and will wait to make sure there are no leaks. The directions say it could take up to 7 days for the joints to expand and fill all cracks that could possibly leak.
After I have determined it has no leaks, I want to add some sulfited water in it to make sure there is no bacteria in there before the wine goes in.
Here is the one I'm using this year. It is 20L, or approx 5 gals: