missing water

hi ,Im new to this,    on 19 oct, my husband and I came down stairs, and found his marine tank , nearly half empty of water, that is 18 gallons, the floor was dry ,after checking everything was still tight , the tank was refilled, no leakage, the only thing wet ,was a newspaper under the filter below the tank, my flooring is laminate and was completely dry ,and nothing to suggest, that the water could have got under the laminate ,at the edge, by the skirting  ,as of to today, 23oct ,no sign of the water,     anyone have any ideas ? kay