You change the water by at least 30% every few days. It is far more frequent than would be needed for the same fish as adults. For a tank only running 5 weeks, you may not yet be cycled and the water changes may need to be even larger and more frequent if your ammonia or nitrite levels start to rise at all.
Fry produce very little waste and not that many water changes will be needed.
I would do a 30% water change every other 3 days, frequent water changes on fry tanks also help them grow faster.