This is a general hint!
Holothuria (Thymiosycia) arenicola has a harmful toxin.
As a rule, animals with a harmful poison do not pose any danger in normal Aquarieaner everyday life. Read the following husbandry information and comments from aquarists who already keep Holothuria (Thymiosycia) arenicola in their aquarium to get a better picture about the possible danger. However, please be careful when using Holothuria (Thymiosycia) arenicola. Every human reacts differently to poisons.
If you suspect that you have come into contact with the poison, please contact your doctor or the poison emergency call.
The phone number of the poison emergency call can be found here:
Overview Worldwide: eapcct.org
Translated with www.DeepL.com/Translator
Correct name converning WoRMS:
Holothuria (Thymiosycia) arenicola
Correct name converning Sealifebase:
H. arenicola is a cream/white-coloured species with a double row of dark red spots along its upper surface. It is small to medium sized (up to 300 mm.), long and cylindrical, sometimes sand covered. It is a rigid species with a tough tegument covered with small, hard papillae. Cuvierian tubules are vestigial. The spicules are small, square tables, and buttons with rather small holes (H. arenicola spicules). This species may be found on reefs and in coastal waters, usually in the sand below rocks.
Remarks: Colour and pattern serve to distinguish Holothuria (Thymiosycia) species when alive. Spicule form must be used to clearly distinguish H. arenicola from H. (Lessonothuria) pardalis or even H. (Cyslipus) rigida with which it shares a superficial similarity of form and habit.
Source: Marine Species Identification Portal