How can you create a combo with Earthcraft, Fertile Ground, Horseshoe Crab?
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[START OF COMBO]This combo can be formed with Earthcraft, Fertile Ground, Horseshoe Crab

Color identity: GU
Mana cost: 
Steps:
  1. Activate the basic land with Fertile Ground attached by tapping it, adding at least {1}.
  2. Fertile Ground triggers, adding {U}.
  3. Activate Earthcraft by tapping Horseshoe Crab, untapping the basic land.
  4. Activate Horseshoe Crab by paying {U}, untapping it.
  5. Repeat.
  6. If the basic land is an Island, you may add mana of any color using Fertile Ground's trigger, and you may infinitely repeat steps 3-4 with any other basic land you control.[END OF COMBO STEPS]

Result:
  - Infinite colored mana
  - Infinite untap of basic lands you control[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - All permanants must be on the battlefield
[END OF COMBO PREREQUISITES]
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