Is my tank good to go?

I have set my new 450l (120g I think) tank up. I have taken 5 small gold fish out of my pond to cycle it. I did have a piece of sponge in my other tanks filter for about 3 weeks to get bacteria on it and a handfull of seachem matrix in there aswell for about a week. I have put the sponge in the new tank and the matrix in the new canister filter. After 3 days only, I have done my first tests, ammonia was 0, Nitrite was 0 and nitrates were 5ppm. Does this mean my tank won't cycle and is good to go or should I wait a few weeks? Also the Ph is 7.2 which it was when I put it in, so this hasn't altered, which I thought happened in a cycle.

 

How long did you have the goldfish in the tank? 3 weeks or the last 3 days only?

 

I had the sponge in my 4 year old tanks filter for 3 weeks. The goldfish have only been in the new tank for 3 days. Is this long enough to produce ammonia?

 

If you have 0 ammonia, 0 nitrites, you are cycled! Looks like you are!
Your media probably gave it a good boost!

 

After 3 weeks with a filtersponge from an old tank, my guess is like jwebbe: you are good to go.
3 days isn't much, but goldfish are messy feeders so it should be enough - if you still have 0 ammonia and 0 nitrites ... yor are good to go! And very low nitrates - good. But bioload is low, too (even with the goldfish), so you should monitor nitrates every time you add new fish (day-after), nitrites and pH weekly for a month.

Change all the water, arrange the plants if needed, and wait a few hours for the temperature and chemistry to settle in. Slowly add your fish. Slowly means weeks.
And don't forget to use a quarantine-tank with new fish...