I also used UGF in the late 50s and early 60s (they were called Miracle filters back then), and on similar sized guppy tanks, and back then, (but without any additives), they did fine, bred like rabbits, Even though, then, water changes were thought to be bad.
I believe many keepers in MFK have fish that sh't almost as much and at a volume, as we humans do, and other than vacuuming it out (I vacuum every other day, sometimes every day (as a rule)) any help breaking it down is a blessing.
The subject of probiotics in aquariums, has nothing directly to do with fish food.
It is about waste treatment, and competition against pathogenic bacteria.
And for "me" the primary use (focus) was the completion against pathogens, and other nasties like cyanobacteria, and columnaris (which lives and can have a latency period in detritus) was my main focus.
Way back in the thread maybe 30 pages, I posted photos of my experiment using Rid-X to reduce those same cyanobacteria.