Just make sure you check everything with a good test kit before adding anything.
Add all your water first and use some prime to make sure there is no chloring.
I left the prime in there for 30 minutes before setting up the filter.
Then started that up.
Everything went fine.
I put the fish i had in my 7.5G straight in (once the water cleared a bit) and they had no problems at all.
No ammonia spikes or anything.
Just be careful cause mine might have been a fluke so make sure you check everything thoroughly.