10.22376/ijpbs.2019.10.1.p1-12 Volume 8 Issue 4 2017 (October - December) Sponge is one of the marine organisms of coral reefs that is able to produce secondary metabolite compounds with varieties of bioactivity and structural variations; one of its biological activities is as an antimicrobial. This study is aiming to test the bioactivity of lessThan i greaterThan hexa-tetracontane lessThan /i greaterThan compounds that have been isolated from sponge of lessThan i greaterThan Callyspongia pseudoreticulata lessThan /i greaterThan . An antibacterial activity test was performed on the lessThan i greaterThan Ralstonia solanacearum lessThan /i greaterThan bacteria found in potato by using agar diffusion method with the use of filter paper discs. The result of bioactivity of lessThan i greaterThan hexa-tetracontane lessThan /i greaterThan compounds with varied concentrations; 400mg/mL, 500 mg/mL, 600mg/mL with incubation periode of 1 – 7 days, showing that the diameter of the inhibition zone is at the peak of the bacterial growth under the concentration of 400 mg/ml and incubation period of 7 days and the diameter of inhibition zone is lessThan i greaterThan 21,33 lessThan /i greaterThan mm with great difference compared to the other concentrations. M. NURDIN AND USMAN Bioactivity, Hexa-tetra contane, Abtrivacterial, Callyspongia Pseudoreticulata, Ralstonia solanacearum. 183-186