I am setting up a 180g tank with built in overflow and ramp/platform for freshwater turtles.
(posting here because general setup seems most similar to reef tanks)
I have 3 red-eared sliders in a 45g with Fluval 405 set up now, the 180g is new and needs another week for the seals to harden. I hope to have everything set up by then, Saturday the 27th.
I have drawn up 2 options for the undertank setup and would love feedback on:
·Water flow through the system in general?
·In case of power outage, would these setups lead to flood?
·What type of plumbing, rigid or flexible?
·Water pump, submersed or external, what brand?

setup1
or

setup2
If pics are too small, also attached,
Thanks for looking