They will need room (probably more like an 8' or 10' round pond for the adults), especially if you are hoping to breed them. Sexual maturity is usually close to 3 feet on those.
If you are getting them, I'd set the pond up first and getting it running well. Guitars don't often do well in young/new systems. They are a fairly heavy bio-load, so something that has a strong and stable aerobic bacteria colony already going is your best bet.
They are awesome fish to have, but definitely take your time and get the proper set up to house them in.