A Fuzzy Dwarf Lion shouldn't be put in anything smaller than a 40+ gal
tank anyways unless you have very powerful filtration (high quality skimmer) and are dedicated to 15+% pwc
Most sites state a 30 gal
minimum but Lions are messy eaters and need the extra gal
to avoid contaminating the water too quickly.
As others have already mentioned this fish can easily consume fish near it's own size so anything smaller than 4" would be fair game eventually.