So I shouldn't plum it to and from my sump?
By way of example:
I have three frag tanks that share the same water system. Started with just one. Each time I added a new tank, THAT tank would get dinos. The old one(s) did not show much if any dinos.
Dinos are free swimming protists. They prefer to remain where they know the light and food is going to be. Sure, some will make it to the overflow -- and a blackout does encourage this -- but zap them where they live.