There are three times the number of tadpoles as frogs, so there are 3 * 5 = <<3*5=15>>15 tadpoles.
Two-thirds of the tadpoles will survive to become frogs, so 2 * 15 / 3 = <<2*15/3=10>>10 tadpoles will grow into frogs.
When the tadpoles grow up, there will be 5 + 10 = <<5+10=15>>15 frogs in the pond.
The pond can only sustain 8 frogs, so 15 - 8 = <<15-8=7>>7 frogs will need to find a new pond.
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