[Grandpa Kim]

I have never had luck with blockading so these are just ideas.

Setting both the fleet strategy and the ship strategy to "Don't get hurt" should work. The problem is your ships strat is set by ship design, not by individual ship. Most likely you have your ship designs spread through several fleets and you certainly don't want to cripple your ships in more active fleets with a "Don't get hurt" order.

One thing that might work is to set your fleet orders to "Don't get hurt", "Do not break formation" and "Don't fire on planets", as others have suggested BUT select as your fleet leader a ship that has "Don't get hurt" as its primary strat. IE. a repair ship or minesweeper. This should cause the leader to drag the fleet off to a corner and your attack ships should only fire on targets that happen to come in range.

I've not yet tried this, but it should work.