Amphipods are shipped in jars containing a reef-safe nylon sponge. The amphipods are strongly "benthic," meaning the prefer a surface to cling to. They tend to burrow deep inside the sponge due to the stresses of shipping. We suggest adding all the water in the jar, and placing the sponge in the sump or tank for a couple days. After a couple days, the amphipods will have migrated out of the sponge in search of food, and it can be removed if you'd like. Please note that we intentionally fill the amphipod jars only about 1/3 of the way full with water. If part or all of the sponge is out of the water, it's perfectly fine.