The Tetra Whisper Hang on back (HOB) filters are okay. The usually last a long time and are quiet. Unfortunately the filter media for the Whisper is tiny. The sponge for growth of beneficial bacteria is less than 1/4" thick and there are only a few grams of activated carbon. This doesn't allow for very good filtration of the water as there is little space for the extremely important biological filter, beneficial bacteria. It does filter out large particles reasonably well, but that is about it.
Their new line of internal filters, which are designated with an i (as in Whisper 10i) are pretty bad. They take up a lot of space within the aquarium and they allow a lot of bypass. That is a lot of water can move around the filter media and nothing is removed from that water. This filter also has the problem with the other whispers in that it has very little filter media. Also my newt liked to crawl inside of it for some reason. There is no access to the impeller, but I still didn't like that.
I would recommend an Aquaclear filter first as these tend to be long lasting and they have a lot of media that is much harder to bypass. Their prefilter sponges are large bricks, the carbon bags for them are much larger and they also come with porous ceramic cylinders for biological filtration. They have tons of microscopic spaces for bacteria to grow in. Don't ever throw that part out!
The other good filter option that I have seen for Hang on backs is the Marineland Penguins which provide a lot of space for biological filtration due to their biowheel. Marinelands tend to have smaller more expensive media cartridges as a downside.
