How do I remove hardwater and/or bark stains from concrete?

Question:I just had brand new colored concrete put into my backyard. We put planters in one section and the drip system was on too high and water has been seeping out from underneath and staining the concrete there a reddish brown color (i'm assuming from the bark). I also have a section where the water doesn't drain all the way and I'm getting white cloudy staines, which I'm assuming are hardwater stains. Any ideas on a stain remover or way to brush it where i don't hurt the concrete? Thanks!

Answers:
Use trisodium phosphate, which is sold in most hardware or home improvement stores under the name "T.S.P." It should work well. If you need elbow grease, patch test using a wire brush to scrub. The TSP shouldn't hurt your colored concrete, but since I don't know whether your tint is a surface treatment or throughout the concrete mix, I'm not sure about the wire brush.