The tank will cycle fast with two goldfish which are massive waste producers.
The filter won't cope with the load soon, so I would take them out now.
Its 20 gallon for the first goldfish then 10 gallon for every other goldfish added.
Plus double the filter size to the tank.
oops yes 20g for the first fancy. but the common goldie tank size was correct and i am sure you will agree its an important difference.