Last week after only a few days in the tank, one of the seahorses made it past the overflow. Put a screen on it. Following day, I couldn't find the other horse. She got past the screen, including a couple baffles, three elbows, the hard turn in a t, a semi closed valve into the sump. Happily hitched to the heater when I found her.

She's just fine. Makes Finding Nemo not all that far fetched.