Is it so mysterious?!

A fascinating update for y’all… Two kind people on the aquariumadvice site have suggested what my Mysterious Matter may be: the remnant of a piece of fish food, apparently common in new tanks or a hard water deposit.  I have tested my pH and don’t think it is the latter.  To save boring the world further, I may just get my arm in there and wipe it off!  I hope it’s not a higher life form.

Happy weekend