U could probably float the bag of mushrooms and add water by cup over time.....but u said theres an emerald crab and all inverts are very sensative and need long acclimation, therefore if i were u i would drip acclimate both anemone and shrooms/crab, take a bucket and dump the bag in it. If the water is too shallow lean the bucket using a prop such as a phone book and lean it on the stand etc so that tge water goes to an area deep enough for both items to be senerged in water...then take a airline and siphone it to the bucket( one end in the tank, suck on the tube so that water starts to siphone and then place in bucket) then tie the airline in a knot so that u get one to two drops per second, let it sit for about 2 - 3 hours and your good....btw your going to need saltwater to replace the used water