It will provide additional surface area for bacteria. Nitrification bacteria will remain at the level in proportion to the amount of ammonia in the tank. If you have reason to suspect ammonia issues, then providing more room for bacteria is fine; but unless the tank is way overstocked there should be sufficient surface in the aquarium for the bacteria. They colonize every surface under water, the grains of substrate, tank walls, plant leaves, wood, rocks, and of course filter media.
You don't mention plants, but if it is a planted tank I would not recommend encouraging biological filtration as it is likely detrimental to plant growth.