You will need more than just a 75 micron net, you will need a conical plankton net to do this here is instructions how to do it yourself
net
Probably the last hour of an incoming tyde is the most desirable, the only issue that you need to be aware is that you could also catch undisarable organism in to your net and introduce them to your tank, hopefully, most them will die in the freezing process.
Good luck