Hi Tricia,
It looks fantastic - After seeing the first picture I thought it was going to finish up quite contemporary with a statue of the Venus de Milo or something in the middle - I always think that those time-lapse photos when constructing something look great. However, I do think they portray an illusion that the steps just seem to flow from one to another without ever showing just how much time and effort goes into every stage.
Could you perhaps plant a couple of tallish marginals near the filter? I had a Water Mint last year, which grew about two tall. I’m sure there are many others, which do the job as well.