Plagron has a wide range of additives. UNIVERSAL These products can be used on all substrates and compatible with all fertilizers. UNIVERSAL products are divided into boosters, enhancers, protectors, pH controlers, substrate complements and starters. Each product type is identified by an icon on the back of the product, for example, an arrow or asterisk. You can recognize UNIVERSAL products by their purple label. Biological additives are distinguished by the CU logo on the packaging.