Re: Bulkhead, slip or threaded?
If you are worried about clogs that cause the water level to rise, you could install a float switch at the maximum water level and use it to shut off the return pump. Will there be a sump? If you use a canister filter, then there's no worry of overfill from a clog (though a clogged canister can itself get damaged).
I think I could turn and live with animals, they are so placid and self-contain'd.