Indecomposable optimal entanglement witnesses in C4 {otimes} C4

We provide two 1-parameter families of indecomposable entanglement witnesses in C4 {\otimes} C4. Following recent paper by Ha and Kye [Phys. Rev. A 84, 024302 (2011)] we show that these EWs are optimal and hence provide the strongest tool in entanglement theory to discriminate between separable and entangled states. As a byproduct we show that these EWs detect quantum entanglement within a family of generalized Horodecki states.