could i just a 10 gallon fish tank to be a hydro system for two plants ???
and a small pump that always make the water flowing???

Well, yes. If you try this, do some research on dwc. Filthy fletch is the masterbuilder of them and can probaly tell you how you could set it up for it, Maybe give you some ideas on reinforcing joint etc. It is doable. You will have to cover the outside of the tank so no light shines thru, Major Toke posted a material he used to accomplish this. You don't want light to get in there. Ask Fletch what size of pump if you go with his aero set up. I don't think he recommend small ones for that. VV