Was going to post some links, but I'm not sure on the rules about that on the forum. It's pretty simple once you understand how they work. do some googling, you'll figure it out lol. I made mine from empty fish food containers, ugf uptake tubes and sponge. You have to use a certain type of sponge though.
haha that's true. They are only a few dollars. I had to make mine because none of my lfs carry mine. I didn't want to buy something off the web that would cost more to ship than the item itself cost lol.