There is a great need for developing of eco-friendly antifouling biocides since negative ecological effects have been proven for current antifouling biocides. In the present study acute toxicities of potassium sorbate (KS), tannic acid (TA), copper(II) sulphatepentahydrate (CS), Caulerpa prolifera extract (CPE) were investigated on the survival of A.salina. LC50 values were found for KS, TA, CS and CPE as 19.96 g/L, 155.30 g/L, 10.47 g/L and 20.40%, respectively. In order to investigate the antifouling performances, the biocides were immobilized into phytagel and submerged into sea for one month in inner bay of İzmir. In conclusion, slightly dissolving versions of studied eco- friendly biocides could be replaced with copper based antifouling biocides.