First one, Xenia for sure
Second one is a nudibranch, not a slug. I'm not certain which nudi you have there as there are thousands of different types. It looks a lot like a Lettuce Nudibranch in body structure but it doesnt have the green coloration of the Lettuce Nudi. It COULD be a coral eating nudibranch, but its tough for me to tell as I have little direct experience with them. Some useful facts about nudibranchs:
- They all have very targeted diets. Nudibranchs will eat one or two food items and no others. In the absence of their preferred food item they will perish.
- Some are coral eating nudibranchs, others eat anemones, still others eat algae or dead matter
- If they consume corals, anemones, or other invertebrates that sting via toxins or nematocysts, they will concentrate these toxins in their skin. If/when they die, they will release those highly concentrated toxins into the water column and CAN "nuke" a tank (kill most life within). Also because of their ability to concentrate toxins/poinsons, DO NOT, I repeat, DO NOT squish them with your fingers or otherwise come in contact with them with your own bare skin. Anaphalactic reactions can result quickly from dangerous nudibranch contact. Always use gloves if you need to handle an unknown nudibranch.
- The general rule of thumb is that cream colored, dull green colored, or otherwise boring looking nudibranchs are NOT poisonous. It is more often the case that small and highly colorful nudibranchs are dangerous.
In short, some nudis, great. Others, bad.
