For first month you are going to get away with it just fine I am sure but after that, if all goes as it should, you going to want to change the nutes every week as she is going to suck in all the water super fast. I remember at the peak generative period my AutoUltimates could suck in around 5 litres a day so I had to add another bucket with same nutrient blend to even maintain the reservoir level every now and then. But you can try to just top up the reservoir and do complete change every two weeks if that suits you. It might work for you just fine and save you a little bit of juice.