Research goal: The aim of this research was to evaluate a natural product with acidifying activity on plant growth and the effects on rhizosphere microfauna in ornamental succulent plants. Materials and Methods: The experiments, started in July 2021, were conducted in the greenhouses of CREA-OF in Pescia (Pt), Tuscany, Italy (43°54′N 10°41′E) on Tacinga imoneana, Euphorbia submammillaris, Marlothistella uniondalensis and Cotyledon ladismithiensis. The experimental groups were: i) group control in peat, irrigated with water and substrate previously fertilized; ii) group control in compost, irrigated with water and substrate previously fertilized; iii) group with organic acidifiers (organic acidifying product by Fertalis srl) in peat irrigated with water and substrate previously fertilized; iv) group with organic acidifiers in compost irrigated with water and substrate previously fertilized. Results and Discussion: The trial showed a significant improvement in the agronomic parameters analysed on Tacinga imoneana, Euphorbia submammillaris, Marlothistella uniondalensis and Cotyledon ladismithiensis plants treated with an organic acidifier. In particular, there was an increase in plant height, vegetative and roots weight, flowers number and life. In addition, the experiment showed that in theses treated with the organic acidifier, there was a pH lowering and a significant increase in the substrate microfauna. Conclusions: According to the results obtained in this study, the application of a natural acidifier in peat-based substrate or compost can be useful for increasing plant productivity and soil microbiology.