I usually answer your computer questions, but this will make
for a nice change of pace... ; )
30 minutes on high seems more than adequate to cook even
lobster in the shell, but I'm thinking you're going to be
adding shelled lobster meat. 30 minutes is a long time,
for fish. Shrimp can be boiled in about 3 minutes, and
scallops would be about the same. Halibut shouldn't take
more than about 7 minutes for 1-inch thick fillets.
Lobster in the shell can be boiled in 18-20 minutes.
All of this is relative, and depends on several things.
Are you adding frozen items or fresh? Fresh will take
considerably less time than frozen, and the times above
are for fresh. Does the recipe call for you to wait
until the water reaches temperature after you turn it
up, or to simply turn it up and add the ingredients,
so that the half hour includes the time it takes to
reach a higher temperature. The latter makes more
sense to me.
This cioppino recipe, for example, calls for the following
amounts of fresh ingredients, and calls for cooking all of
them for only 7 minutes after adding them:
"1/2 lb. medium shrimp
1/2 lb. scallops
24 fresh mussels
1 lb. firm white fish"
If it were me, I'd definitely want to avoid overcooking
the seafood, which would make it tough, especially the
shrimp and lobster. My approach would be to turn the
heat to high and then wait the time it takes to see it
simmer at a greater rate.
Then, assuming you're adding fresh, shelled lobster meat,
I'd add that first, and let it cook for about 10 minutes.
Then I'd add the halibut, and wait about 5 minutes until
it looks like the halibut will flake easily with a fork
about 2 minutes later. Then I'd add the scallops and the
shrimp and check it again in about 3 minutes, at which
point the shrimp should no longer be translucent, but
solid white with orange, the halibut should flake easily,
and everything should be done to perfection. The chef's
perogative to taste test the seafood should be employed
at this point... ; )
I'd remove it from the crockpot at that point, to avoid
overcooking from residual heat, and let it rest in a
covered container until serving time.
Darn...now I'm hungry!
If you have further questions, don't hesitate to ask...
Additional information may be found from an exploration of
the links resulting from the Google searches outlined below.
Searches done, via Google:
lobster boil minutes
boiled shrimp minutes