Yep, what he said. Have a look at your current system and how all the parts of it work etc, and also have a look at other hydro setups people use and try and understand how all the parts of them work. Then have a look at your grow room, requirements, and restrictions, and plan out a system that works for you. If you can buy something pre fab that suits, great, if not, save yourself some money and build one to suit. Bunnings sell stuff like pond pumps, poly tube and fiitings etc, but they don't sell outlet/inlet fittings so I get them from hydro shops. They used to sell Tuffman storage tubs which are made of plastic that doesn't go brittle and crack when drilled etc, but stopped stocking them, so if you want to use tubs be sure to find some with that thicker more flexible black plastic. Pet shops are a good place to get water heaters, and some aquarium pumps are also good for hydro. Plenty of options out there, you just need to figure out how you want to grow and what setup will facilitate that first.