I'm curious on everyone's favorite hang on back filter. Include pros/cons if you can. I currently have 4 tanks, and on my 40 gallon I decided to try out the Marineland Penguin 375 a while ago. I also bought a Penguin Pro 375 for my 55. The pro mostly seems okay, but I am paranoid that the tubing is going to fall off the pump since it doesn't fully click in (which I have read is a common issue). I have 2 more smaller tanks (10 and 20) that have the smaller versions of them. However, at this point, they are driving me insane. A couple don't prime very well no matter how much water I pour in them. My 375 is loud and rattles now. I tried cleaning it out, including the impeller and reseating it to no success. The biowheels, well whatever, they're there lol. I'm currently considering the Seachem Tidal filters, my only drawback I see with those are of course the price and the fact I can't turn off the surface skimmer. I also like HOBs that have decent room for extra media. I use my own filter floss, sponge filter, and Seachem matrix for biological growth. I wouldn't be buying premade filters. I did have an AquaClear on the 20 gallon in the beginning, and I know many people like it and I love the media room, but they never ever re-prime themselves which is why I took it out of service. So with that being said, what is all of your favorites?