Book-learning alert - I don't have any crucians to fish for, AFAIK.
But, back in the late 1800's, the debate raged about what to do about the "Fine" bite - the slight change in the float's movement which, if struck, often yields a big roach. Allegedly.
J. Greville Fennell, the information hub of the debate, and an understander of Archimedes' principle, experimented with a reversed porcupine quill and found it
too sensitive; others went the other way and fattened their float tops by cutting the top off a quill, using thicker float caps, or both - and had some success.
Having watched goldfish and roach feeding, I suspect that the Fine Bite was a perfectly confident take of the bait by a fish which was in no hurry to move on, so a float which made a ripple at the first tiny dip that brings the cap into contact with with the water's surface gave a better indication, meaning one you could actually hit.
As an added benefit, they
may also have alerted the fish to a vague need to be elsewhere, which may lead either to an even better bite, or the fish spitting the hook out.
Further investigation along this line may just be worth a go...or not.
With the current state of my eyes, it seems worth a try.
By the way, Fennell's correspondences are in his "Book of the Roach", which is out of copyright and can be found free online.
Here, for example:
The book of the roach. - Full View | HathiTrust Digital Library | HathiTrust Digital Library