I bought a 125 aquarium from someone and it came with all sorts of items. It used to be a salt water tank. I have cleaned it so that I can use it for my piranha - fresh water. Along with all the other items there was a Hydor Koralia 3 pump (?). I have been looking for information about "what" this is and how it is to be used but can only find them "for sale". Can someone tell me what I would need to know about this product?