What type of detergent should I use in my GHD3800?

Use only detergent specifically made for use in dishwashers. Cascade® Automatic Dishwashing Detergent has been approved for use in all GE dishwashers. Keep your detergent fresh and dry, and don't put powder detergent into the dispenser until you're ready to wash dishes. The amount needed depends on water hardness—hard water requires extra detergent while soft water requires less. (Page 13)