Blopple's (first ever) IM 40L AIO Build

[Buckeye Hydro]

That would make life easier for sure. I think I need 1/2 though? I'm not sure honestly.

Only one way to find out. Unscrew that flexible hose and try to screw on a 1/2" fitting and a 3/8" fitting and see which works. Plumbing fittings are a bit deceiving in that (for instance) 1/4" male threads measure more than a 1/4" outside diameter.