Collection of 'watery' fish waste

Hi! We usually collect fish waste from the fish market down the road every weekend. It comes with quite some water and blood as a result from the cleaning and rinsing. The liquid amounts to about a liter over maybe 6-7kg of solids...Shall I leave the liquid and mix it with sugar together with the solids? Or better to strain the water and use only solids from the fish waste? Thanks!