I can only speak from my own first hand experience;
I added 3" of dry SMS to a 12x24" tank full of shrimp
and snails, from the bag without rinsing it. I gently
sprinkled about a pint of SMS at a time so it would
lightly rain down giving the shrimp time to move away.
SMS is light weight with a lot of air trapped in it's pours
so it falls down slowly like fish food pellets in water.
The tank water got dark gray, but cleared up after
only a day with regular canister filter and rinsing of the
filter sponges. when I pushed plants into the SMS two
days later, I kicked up some of that fine settled dust,
and released a lot of air bubble trapped underneath,
but it would dissipate after only a few hours. If you
don't trust what I've written will work for you, then
just try it in one corner of your tank and if a day later
you get the results I've described, do the whole tank.
I doubt I lost any shrimp, and whatever snails I may
have buried were Spixi's, so they emerged just fine.
I'm so glad I didn't waste energy rinsing this stuff or
removing my tanks inhabitants first, and would do it
again even on a far larger tank with gilled fish. just
wait a day before planting the tank, or you'll get the
black SMS dust all over your plant leaves. because
you tank has not cycled yet, you may still see a white
haze for a week or two after, but that has more to
do with biological filtration than using dry SMS. to
reduce the duration of that white haze, use a already
biologically active used media filter, transfer some
mulm from another active tank, or get a few pouch's
of new tank starter solution like BIO-Spira.
180 tank will require 3 bags of SMS, you could slowly
dump it directly from the bag into one end of the tank,
so the fish will gravitate toward the far end, then
spread it around with your hand or a spade/spatula.
I also used a plastic ruler to get it all nice and level,
but had to do it mostly by touch since I could not
see through all the black SMS dust. it's best to get
the grade the way you want it that first day, since
doing it a day later will only kick up the dust again.
the dust will not settle on the SMS surface, but will
seep into the nooks and crannies between grains, so
don't worry, your water finished SMS will look fine.
if you don't want to overwhelm your fish's gills,
perhaps you could do one bag an hour, rinse your
filter sponge medium, do the next bag, and repeat.