Reef & Rainforest
Nudibranchs adopt one of two survival strategies - brilliant colours to advertise their extreme toxicity, or extreme crypsis (Phyllodesmium rudmani), allowing them to blend perfectly with their food source.
Some polyclad flatworms and the young of one sea cucumber (Bohadschia graeffei) mimic toxic nudi-branchs for protection.
Scanning web sites selling animals for the tropical marine trade still reveals suppliers offering nudibranchs. Many of those listed only feed on specific sponges or bryozoans. The food sources are not offered,so their survival chances in aquaria are zero. As they die their slow death, some species, e.g. Phyllidiella sp. release powerful toxins that poison the entire aquarium. When your local suppliers offer nudibranchs with no chance of supplying food for them, challenge the supplier and report your findings to the local animal welfare groups.