If this is the small filter-feeding yellow cucumber Colochirus robustus, it should be nice to have - sorry, can't find the link, some people are keeping several of them and like it.
I tried to buy such cuke, but when they are contracted and on the top of the tank, the sand-fifting bright yellow cucumber looks the same. Grows big and is better doing with the sand, althouth some are keeping it in bare bottom too (single post at forum, experienced keeper, don't have link right now, sorry).
The nice creature, IME, when it died in the tank crash, there was no evisceration or toxins release of any kind (same with Pentacta anceps pink-green one).
Another possibility is also
filter feeder, Pentacta lutea. I had only its pink relative, Pentacta anceps, and really like it - gorgeous animal.
Interesting to see, how they "lick the fingers"
No problems, worth to have, only have to be fed all the time (~8 times a day), that may require effective skimming for a cleaning.
