The addition of Hydrogen Peroxide (H2O2) in pure hydroponics systems can result in the improvement of the crop by oxygenating the fertigation nutrient solution (NS), among other benefits. We studied the effect of different doses of this peroxide on the size of pepper fruit (Capsicum annuum L.). Gauges are set according to the Ministry of Agriculture Policy in the BOE, corresponding to the trasposed european rules for fresh green pepper consumption, Regulation EC No 1455/1999 of the COMMISSION of July 1, 1999. The results show that Level 1 (0.75 mMol/L) behaves as the Test; meanwhile, 1.50 mMol/1 has a minimal size effect. The Level 3.0 mMol/L decreases the Level 1 but increase notably Level II and Destri. The recomendation is not to exceed 1.50 mMol/L concentration in nutrient solutions.