What Do The Gel Bracklets Mean How Do I Repair A Diesel Truck That Has Gelled Over?

How do I repair a diesel truck that has gelled over? - what do the gel bracklets mean

I know there are anti-gels on the market, and know (now) to prevent the mixing of diesel fuel No. 1 and No. 2, the gelling agent. However it happened, and I need to know what I do to fix it, and if you're a costly repair.