hi i saw a tank last nite where it had bubbles coming from the bottom of the tank up what makes this happen and where can i get one from and how does it work
it could be one of several things. all, well most, of which are powered by an, air pump. these cost from £10-£40 depending on, power, brand and, unfortunately, where you buy them. the parts you put in the tank, are called Airstones,bubble/air curtaines. you connect them to the pump, via clear air line. airstones, are solid objects, anywhere from 2- 12 inches in length costing between £1-£10. air crutains are soft rubber tubes, connected in the same way, but allow you to contour the pipe. they cost, from £10-£25. i find the "air curtain" give smaller bubbles, apart from that, they work in the same way. only warning here, is to check the air curtain you buy, not all come with weights to hold them down.
there are some that are self-contained. the Hydor hydro air colour, for instance. my advice for these, is leave well alone. if you must have one, pop over to my house, i have a Green one you could have with pleasure. it scares the living daylights out of all the fish, when put in the tank.