3 Answers

For an aquarium?

Rinse the coral off and soak it in a bucket of water containing 10% bleach and 90% water until it becomes white.  Rinse it off very well and let dry before putting it in the aquarium. 

coral |?kôr?l, ?kär-|
noun
1 a hard stony substance secreted by certain marine coelenterates as an external skeleton, typically forming large reefs in warm seas: [ as modifier ] : a coral reef.
• precious red coral, used in jewelry.
• the pinkish-red color of red coral.
2 a sedentary coelenterate of warm and tropical seas, with a calcareous, horny, or soft skeleton. Most corals are colonial and many rely on the presence of green algae in their tissues to obtain energy from sunlight.
[Several orders in the class Anthozoa, including the ‘true’ or stony corals (order Scleractinia or Madreporaria), which form reefs, the soft corals (order Alcyonacea), and the horny corals (order Gorgonacea).]
3 the unfertilized roe of a lobster or scallop, which is used as food and becomes reddish when cooked.
DERIVATIVES
coralloid |-?loid|adjective(chiefly Biology & Zoology)
ORIGIN Middle English: via Old French from Latin corallum, from Greek korallion, kouralion .

Dig a huge X across the paddock.Get 2 25foot pieces of pvc pipe,drill holes every couple inchs and place in X pack with gravel so the holes dont clog up and cover it all with sand or clean fill dirt atleast deep enough so when the horse steps it wont crack the pipes.its called a french drain.

Good luck = )