Fixture- Who gets to keep what?

[Josh L.]

In my rental, there's this open loft /room that used to look like this:

Tenants in the past used that space as another bedroom even though its small and didn't have any closets. But, the biggest hurdle to using it as another bedroom was the lack of privacy.

I didn't give the tenant permission to do this, but the tenant went ahead anyways and permanently attached some curtain rods all over that space to hang some curtains:

And, the tenant took down the functional blinds in this space and attached curtain rods and curtains to replace those blinds. 

Since those curtain rods are permanently attached to the walls, does means it has been converted to real property and thus part of the property now? From what I can tell, it would be more trouble than its worth to take down those curtain rods because it would leave all these holes in the walls.

And, if I can keep the curtain rods, are there any cases where I can then also keep the curtains too? If I leave those curtain rods in, then it seems like I'd need to have curtains for them but I don't know how easy it'd be to replace those or if the tenant's curtains are standard size or anything.

The tenant's lease is about to expire. If he re-signs, what could I put in the lease to clarify that the rods he installed and the window coverings in this space are now part of the property?

The tenant put in his own window coverings in all the other rooms too, but those rooms already had curtain rods that he piggybacked on so I don't care about the window coverings in any other room.