Random thoughts...The front and left quadrant looks good and filled in. What're your plans for the back and center right? Rot wallichii may be better if moved a little to the right where it does not have to compete with the Pantanal. Is that Lud simpsonii next to/left-behind the Hygro araguaia? I'd replace that with Limno rugosa, or Acmella, or Bacopa sp (new colorata is nice) or even Lobelia. That spot needs a thick bush of something with round bright green leaves. My choice would be Limno rugosa for it brightness…that spot is a design focal point that needs love. A bunch of Persicaria in the back left would contrast nicely with the Syngonanthus, I think. If you want to be subtle, go with kawagoaenum. If you want a little slap-ya-in-tha-face then Sao Paulo. I'd let it break the surface just a hint.