Leslie is absolutely correct. As I have discussed with you off list, you can specify the date you would like your seahorses to be delivered when you place your order online providing you allow at least a few days advance notice.
However, your new Pixie tank has not yet cycled and it is therefore not yet able to support seahorses are any other life. You cannot order your Pixies on Wednesday because your tank is not yet ready to receive them, unless you were to specify a delivery date at least 4-6 weeks from now, and what would be the point in that? Please DO NOT order your seahorses until your new tank has completely cycled and the biofiltration is established.
Be patient and wait until your new tank is well established and you will increase your chances of success with your new seahorses accordingly, sir.