Upgrading questions

[Pipes1234]

Hi so I'm currently running a 50g reef all lps and softies no sps...and a 55g sump that's about 3/4 full with a full refugium.I recently bought a nice 75g tank and I finished the plumbing and the stand last weekend ....I'm wondering if I were to take the 50g of water from my old setup and the entire sump as is and move it all to the new system than ad a mere 25 gallons or so if it would crash my tank .....never done a big tank move /upgrade before just wondering what others have done or suggest ?
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