You could get shrimp to entertain you , wait till your 50 days in buy two or three fish and put them in a quarantine tank for the last 22 days,
+1... If you're doing a 4 week QT, you really don't have to wait the full 72 days to get fish. The QT is what filled my appetite while the tank was fallow... Not to mention tons if reading on here as well.