I'm trying to replace my small RNA prestain ladder with a much cheaper tracking dye that I can make up myself. Has anyone any suggestions. I run 10% urea-PAGE gels for 75 mins at 300V. I tested Bromophenol blue and Xylene Cyanol recently and Bromophenol blue co-migrates with RNA fragments that are too small so it runs off the gel before it is useful. The Xylene cyanol co-migrated with 30bp RNA which is great. I'm looking for something that will also co-migrate at the 20bp mark too as we use this mark as a guide when to stop the gel. I was wondering if cresol red is useful but haven't seen it used on a 10% PAGE gel. Thanks in advance.