Another option for sand substrates is pool filter sand. Not as fine or as dirty as play sand, and loaches love it, even horsefaced loaches who actually will burrow into it completely. It's rounded, cheap, but is a light color, so surface plants will make the loaches more comfortable by lowering the lighting a bit.
Just rinse it in a bucket (or I used a stainless steel bowl) in the sink till the silt is gone and be sure to let it settle and stir it a couple of times once you've added it to the tank with the water to get the bubbles out. Plants LOVE it, especially runner propagaters, and most fish seem to like it too. It's inert, won't change the pH, and did I mention that it's cheap?
