Sea cucumbers, and their highly specialized relatives the sea apples, can be very beautiful and beneficial additions to any aquarium, but they can also lead to a tank disaster. The cucumbers will expel their intestines if stressed or harassed, which will then rapidly degrade the water quality in the tank. The intestines are quite sticky, so be sure to not touch them with bare hands unless you don’t mind the cleanup afterwards, and be sure to remove them as soon as possible. Also montior the health of the cucumber or sea apple, making sure to remove the stressed out animal before it melts away and nukes your whole aquarium. Lastly, cucumbers have been known to wander into powerheads, much like anemones, and get chopped up. This makes the cleanup process far more difficult and has a far more detrimental impact than simply a stressed out animal.