Are you really considering running a Marine setup in a swimming pool?!
How would you manage heating, evaporation, contamination, predators and the salt bill?
2500l capacity for that pool.
Over 90kg of salt for the initial fill. Times 3 if I'm reading your initial post correctly.
Heating 7500l of water outside in winter would cost the earth.
I imagine you would loose well over 100l of water a day through evaporation.