Backyard Aquaponics
A place to discuss aquaponics

I would say keep it at 50mm.

Yeah either 50 or reduced to 40mm if the fittings are a fair bit cheaper.. I think generally 25 and 40 pipe and fairly cheap because they are such a standard, 32mm can be extremely expensive for pipe and fittings, and sometimes 50mm can be a bit more.. Often depends on the shop..

Not to mention somtimes hard to get.