Is the black triangle between front teeth too small to fix? (Photo)

yes, that's a pretty tiny gap, but there can be some innovative  ways to close it, if it's really bothering you.  Be careful with the bonding though, you don't want to clog that area up and retain plaque, as it will lead to gum issues.  I like to close these triangles orthodontically, but it requires some finesse.  

Bioclear is the best way to close minor gaps, but even this is pretty tiny.  It may be better to consider polishing the contact area to open up the space MORE, then MOVING the teeth together (removable spring aligners can do this).But the space is EXTREMELY small, and many providers may decline taking on the case.