sump pumps

this mite be a silly question but can you use a pond pump in a sump
or would it breakdown due to the saltwater.

Not a silly question at all mate -better to ask than find out the hard way...imo

some of the cheaper pond pumps have steel shafts (the thing the impeller is attached too)which do eventually rust even it the fresh, which would be worse in the salty stuff....

Most these days and for the last 10+ year all use stainless of some grade so would be fine....just remember the return pump is the heart of you system - it stops and......... so spend the money it deserves once funds permit and ensure the water it is pumping is the cleanest, so to stop premature wear of parts....

Have fun !

Pretty much what ignobolis has typed, though all my power heads in use have metal shafts, high-grade stainless metal.

Pond pumps are fine, just check them out, I have hailea pond pumps that have ceramic shafts, they will wear out very fast if abrasive particles can get to them.

But then again,salt is abrasive!

My aqua clear power heads as of the last two, one lasted 18 years the other just under 20 years, but then I use proper pre filtering that isn’t greatly used with most hobbyists, my settling pre filters, they will preserve external bio filtering and power heads for years.