In this small tank, you're reaching your limit. As he matures, he may become more aggressive. If you allow him ample room in the tank, he may continue to be mellow towards your other species.
Keep in mind, it's not always about bioload when stocking a tank, it's about personalities and room to breathe, too.
75: blood parrots, featherfin cat, emperor tetras, turquoise rainbowfish, BN plecos, japanese trapdoor; 46: WCMM, gold inca snails, ghost, bamboo & amano shrimp, kuhli loaches, rummynose & ember tetras, endlers, platies, flame gourami, guppies; 16: pygmy, peppered, loxozonus corys, otos, assassins, RCS ... ~ Research PRIOR to purchase.... ~