ᐅ Should I seal the gap between the stairs on a wooden staircase with acrylic?

Hello,

Our staircase was delivered and installed. Treads and risers were screwed onto a steel staircase.
Now there are small gaps on both the left and right sides.
Is it recommended to fill these with acrylic? (For cleaning and appearance)
Or is that not advisable, since the wood might still expand and contract?

Best regards

Better to use silicone because it is flexible. However, make sure it is compatible with wood. As far as I know, it should not be "acid-curing" (vinegar-based) but rather neutral-curing.