Well beeegbuwds, I'n not a hydro grower, but here's what I think:
I can tell you that you definitely should have a flowering cycle. He must've understood something wrong. You're supposed to veg for as long as you want (some 3-5 weeks depending on strain and conditions) and then have a 12/12 flowering cycle for 8 weeks. It's impossible to harvest a plant after only 8 weeks of growth... even if it were a super fast flowering autoflowering strain...
You should not close the water supply to your plant during the night. But what you should do is to lower the amount of water that will be pumped. If you can't do that, space the waterings out a bit. Because you're growing hydro, you always need to have a water source pumping. Still, during the night, your plant is metabolically slower, so it will not be able to use everything you give her.