Hello, my 29G fish tank is almost cycled. When the cycling does complete (I'm hoping in the next week) I intend to add zebra danios to the tank. I know that you are supposed to have 6 and I intend to get 6 eventually but I've also read you should only add 3 at once. Would it be okay to buy 3 then wait a week then buy 3 more? Or should I buy 6 at once? They will be the first fish in the tank and I have 4 marimo moss balls in the tank (they might help with the levels so I could add more at once).