Fermenting foam for different beers.

I've brewed 2-3 different kinds of beer this year so far and all of them did the same thing, which was have a thick head of foam at the top of the carboy then disappear when the fermentation stopped. But... this latest batch is a strong Belgian beer. At first it had a thick head of foam. But for the last two days, the foam went mostly away, but its still bubbling away furiously. There's a LOT of malt in this recipe. I'm just asking out of curiosity. Is it because there's less hops in this recipe, or because there's more junk for the yeast to eat?

Every beer acts differently.

Ignore it until it stops bubbling, then leave it a week and take a gravity reading.

Trying to predict how a beer is going to ferment, or if you need a blow-off tube is like trying to predict when your next hemorrhoid flare-up is going to happen. Every AG beer I made this year didn't blow-off, until my last batch where I lost almost 1/2 gallon.