You see no values because that array is not a hash table.
When you do
$ergs
you will see all the rows in the array.
To address for example the Pool_id value for the first row, you would do
$ergs[0].Pool_id
The 0 (zero) indicates you want get the 1st row of the array, and in that row you want the Pool_id property.
It's just a matter of knowing the type of the variable and how to address specific properties in the variable.