lol liquid fish? dunno bout that, but you can use any nutrient that has nitrogen will work. you can use unsulphered organic molasses, give it 1tablespoon/gallon. feed it for a few weeks, then ween it off on the last week with 1/2 the dose (1 tablespoon in 5 gallons). you can even give it nitrogen for the first week or two of flowering, but after that ween it off.