I'd expect the loaches to eventually hunt & eat all the shrimp, though you may never see any signs of this during the day or lighted hours.
Fish that were not already living with the clowns, may show a big fish~little fish stress response of constantly moving (even if you never observe any overt predatory activity from the bigger fish), make sure the cories have a place to settle where they are not disturbed by the loaches coming through, also try to create areas of low flow in the tank.
I'd be inclined to separate out some of the fish/shrimp into food grade bins (I'm assuming you have multiple filters or can set up air sponges etc ... all you need is some filter media in a yogurt container with air line flow through) - once the fish are settled into what seems like "normal activity" groups, there'll be less pressure to get the big tank sorted.
You definitely want to remove all sand etc before re-sealing - repeated rinsing, (water) vacuuming to remove all water/sand (tilt tank so water etc flows away from compromised area), drying, then (carpet) vacuuming to remove remaining sand grains .... then do this all over again until you can't feel anymore grit, it just takes time & repetition.
How big is this tank?