You can put fish in there--you can put fish in anything that's holding water. But will the water sustain your fish? The answer is most likely not. Adding fish to a cycling tank is extremely stressful, because your tank is going through periods with extreme ammonia and nitrite spikes--both which can kill your fish in a heartbeat. I would wait AT LEAST another two weeks until you add fish. Or, if you just CAN'T wait to add fish, I would recommend buying Bio-Spira and adding it to your tank. Bio-Spira automatically cycles your tank, as it adds all the necessary bacteria to the water.