I love the design of the AquaClear Filters for a few reasons. It drops water into the Aquarium. The which creates a wonderful waterfall like action while Oxygenating the Aquarium water. Many other filters seem as copy cats. These "Copy Cats" brands often have cartridges in which you do not have the cool option of putt different media in the filter. On top of that you can easily customize your own DIY made media to put into the AquaClear. (I love the most) But second time, since I've had it, I've decided to clean it out. For the first time I noticed there is a little algae growing. I know and understand this is caused by the the balance of my water nutrients along with my plants. As it is a very thin later of the Algae I decided to clean it off with a toothbrush. --- Alright here is the important part. --- I noticed for the first time that the first media, on the bottom, is placed in the area deeper then the propeller spills out water. The flow of the water that is propelled flows upwards as well as outwards towards the media tray display at about the level of the activated carbon. I figured out there is no contraption that pushes the water to each of the filter medias. Water gets pushed closer to where the activated carbon is placed. The media tray which is nicely designed for easy replacements and removal of the media does not help the direction of the flow by directing it. Although it does have mesh parts which allow water to go towards the filter media. Once again this flow only goes flows relatively towards where the middle filter media is placed. From there it does also go in a general direction of up. The issue being that water does not get directed to flow to each one of the medias securely and safely. So It doesn't matter so much that the AquaClear (HOB) Power Filters have such flow rates good flow rates when the media isn't being directed to pass through each one. In conclusion, AquaClear (HOB) Power Filters do not reliably direct water flow though all the medias inside and thus all the Gallons Per Hour flow rate is not a reliable measure of how well the these AquaClear Filters your Aquarium water. I've read on the boards that people want a GPH flow rate of 8x to 10x the amount of gallons you have in your tank. While this works very well in my tank from my personal experience with AC HOB filter. I would think the GPH wouldn't need to by so many times if flow of the water was hitting each filter media. I sorry this post may mostly be a considered more of a rant but I felt it needed to be shared to the many Aquarists whom rely on AquaClears to not be fooled by how it actually filters the water. Although before I edited and rewrote I claimed them not to be reliable but I retract what I said because I do find mine to be reliable. Although my understanding has deepened about the AC HOB filters, I got mad because I thought it was the best thing on the market and to some degree I feel duped because it obviously may be a good filter but not by far the best filter on the market. I guess whenever I get my 20 gallon tank set up I'll try a canister filter.