Excellent, thank you both -
I didn't try the freezer, but I had stored the sodium carbonate solution in the fridge before using it and it froze rather quickly just at that temperature, so I think this situation may be an exception to how the freezer sometimes helps with precipitation.
That gets me thinking, though - if the sodium carbonate raises the freezing point of water, then it should stand that at room temperature, the solution would be thicker and more difficult for things to precipitate out of than, say, distilled water at room temperature - and that maybe if I warm the contents up, that would bring the viscosity closer to distilled water and the harmalas would be able to drop out a little easier...? Thus allowing me to decant and skip the filtering...I really dislike the idea of getting some of the harmalas stuck in the coffee filter. Not that I wouldn't be able to wash them out with water, but it's just a step I'd love to skip.

I think I'll experiment with that first, and if it gets me nowhere then I'll go ahead and filter.
And thank you for the walkthrough on the vacuum setup - I know of them, but it's helpful to know exactly what parts go in to the process. It's something I definitely plan on acquiring in the future.
Much appreciated