i would love some ideas please....

I thought I had my stock for my Amazon tank all planned out, but then I came across pictures of blackwater tanks and that is now the direction I am going. My 29g just finished its cycle (0 ammonia, 0 nitrites, between 5-10 nitrates) and only has 3 neon tetras for inhabitants right now, My planned stock is listed in my signature (I realize the raphael will eventually be a little big for a 29g, but I will have upgraded well before he gets to that size). In addition to the neons, peppered cories, and the raphael I had planned on a male cobra guppy to add some more color, but after some more research it turns out that guppies may not do too well in blackwater environments due to the low pH. So back to the drawing board! Any suggestions on a good Amazonian tankmate that will do well as a single specimen and that is preferably colorful? Thanks!