I'm no rockwool grower, but those are tiny 1cm cube rockwool cubes. I've seen them down the hyrdro shop.....use them in big pots like soil and you can water them manually becuase you use large containers, so they hold more mositure for longer.
You need to provide the nurtients yourself as the rockwool has no nutrional value for the plants. I think you want to be watering at PH 5.5 - 6.0, but I'm sure a more experienced hydro grower will confirm, plus, do some reading up on growing in rockwool....there's loads of good info.
You should check out Arjen's greenhouse seed co. videos on YouTube. They grow in this stuff and give you info on their feeding schedules etc.....could be useful for you. They use like 45l containers to grow in....fucking amazing plants!