I HATE when people say, "it doesnt matter," or "I use tap and I'm fine," every single source of water is different, even the bottled "spring" water from the store will have different ppm levels. It MATTERS, especially in DWC, ESPECIALLY when you start adding Nutes....150 is a good area for seedlings, but what if OP thought it would be okay to take his 200 ppm tap and add Nutes to it?
The OP is obviously a noob, please do not tell them answers that they cannot easily comprhehnd lol