Am i suposed to feel some kind of flow out of 1 of the tubes? when u say set it up after filtration, is it suposed to somehow connect to my fluval?
yeah, you can connect it to our fluval no problem. take your return line and cut in half. the line coming from the filter goes on one end (depends on the model of UV) and the return line going to your tank goes on the other end. so water goes from tank to filter to uv then back to tank.

Once you plumb it in the return line, no you would have to get a new return line to remove it. Why would you want to take it out once you install it?
Should look something like this.so basically i have to cut my outflow tube..so i cant take out the uv sterilizer in the future right? cus my tube is gonna b only half as long