After reading the instructions, installing everything as instructed, I filled it with water and put the plug in and nothing happened. I emptied the water and took the filter off the tank. I was very disappointed it didn't work right out of the box. It appeared the impeller and shaft wasn't seated properly and there's a lot of play in it even when it is seated properly. So I fiddled with the impeller and shaft, got it to seat properly, tested it in the sink, and then put it back on the tank, filled it with water, and it worked. So, hopefully people will read this review prior to installing the pump and make sure the impeller and shaft are properly seated and working prior to filling it with water and putting it on the tank. Otherwise they will be unhappy like I was having to empty the water and fiddling around with it to get it to work after it was already installed. It seems to work well and has good flow and is very quiet.Update: Filter has been performing well and I cleaned it for the first time. It is much easier to clean than my Aquaclear 110's. It isn't quite as powerful, but much easier to handle and keeps my 38 gallon tank very clear. I don't think I would use it on my big tank though because it doesn't have quite the power and flow that the 110's have. Good alternative if you want to save yourself time and trouble cleaning the Aquaclears.This review is for my initial use of the #20 Cascade filter. I promise I will update, if my expectations go south. I am using this filter in a 15-gallon rimless tank that already has a sponge filter in it. There is little water movement with the sponge filter alone. Now, the water flowing from the Cascade is slightly moving the leaves of a Crypt about 20 " away. This is wonderful.My tank is 3 1/2" form the wall. This gap limits what filter can be used. Also, my glass top allows for just 1 1/2" for the spillway. This Cascade works just fine with those measurements.As far as noise goes...yes, there's some when it first primes itself, but after it gets going the noise virtually stops. I did remove the top though, because it did rattle a bit. That may have been the noise some reviewers complained about (?). Very satisfied with the results.I added my own mix of media with floss as the last material the water passes through. The filter body is transparent giving you a good indication when the media needs changing. Like that.It's critical to always have water in the motor's side of the filter before plugging it in. Otherwise, the motor will burn-out pronto. This is the loudest time as the motor goes to work filling the filter box. This noise ceases once the box is full. Also, just enough water remains in the motor's compartment-side when the filter is turned off making a safe restart possible. This has been my experience since I have the filter on a timer.The plastic has a solid feel to it, and its blue color has a warm ambience. That's a bonus.So, this is only the beginning. What's up ahead?I was looking for a tiny filter for a small tank and Amazon was the only place I could find what I wanted, even specialty stores didn't have the size I was looking for.I like that flow rate is adjustable, and at a low rate is quieter than any filter I've used in the past 20 years.So easy to put together and start,b lower/ higher actually works like it says, quiet too. well worth the money, thanks will be looking for your products when needing supplies. Thank you!This filter does well in all aspects. The filter element is a preassembled model, haven't been able to find a cheaper, reusable version of the filter, but everything else is good.I decided to switch to this filter for my 62-gallon fancy goldfish tank after running a Marineland Penguin for quite some time... it was the best decision I could’ve made.The biggest pro to using this filter is the silence. It’s the quietest hang-on-back filter that I’ve ever come across. 4 months in and there’s little to no mechanical noise coming from the motor, my mother often puts her ear up to the filter because she can’t believe it’s even on. There’s also very little noise created by the water return (which I absolutely love). If you’re someone who likes to hear the sound of running water this filter will not be it for you, you can hardly hear a trickle.The filter is also incredibly efficient with a fantastic (and completely adjustable) flow rate. They really don’t lie on the box when they say this thing turns over 300 gallons of water per hour. Be prepared to have your water looking clear as day, especially when used with the right filter media.My only concern with this filter is that the materials do feel a little bit fragile, so I’m curious to see how it holds up long term.All in all though, it’s fantastic value for the cost; it’s just as good as any other mainstream brand filter out there.I have this on a twenty gallon tall that is growing my Porcupine Puffer and Blue Wrasse. It fits perfectly on the short side after your alter the little tabs. its the exact length of the 20 gallons width as well which makes the fit look great. The filter pads that come with it are great for a week or two after that buy your own pad and clean/replace that instead of the one that comes with it. I left the bio sponge that came with it. I used the vent holes to run an air line. the way the filter flows and the air stone sits it kinda acts like a crude skimmer, not intended but a plus for my messy eater tank.Please . I have been trying so hard to look for the missing part I need. For my filter.. I received this package on April 16th. Today me and my husband were totally excited to set up our new tank using this Cascade 300 filter. The Strainer cup (Part H) CPF507 part did not arrive with this package. Whom do we contact or where can we order this piece we need?EDIT - Almost one year later to the day and I have just had to purchase a new filter to replace this. As mentioned in my original review, this filter tends to stop on it's own more often than I'm used to after years of AquaClear use, and after discovering it stopped two days ago I haven't been able to keep it going. Turned back on for a day, then shut off again. Just tried cleaning/fixing now, and it turned on when plugged in but stopped again before it was even primed and running. As my first experience with this filter, I won't be buying again.I have purchased two of these Cascade HOB filters now in two different sizes. I am very much a die-hard AquaClear fan and have been for about 20 years, but the AC's have a very short overflow lip (where the water flows out of the filter into the tank). I have a fish tank in my living room and the AC overflow only reached the surface of the tank water if the tank was full absolutely all the way to the top - after a day or two of evaporation, the overflow on the filter was higher than the surface causing a waterfall that created more noise than I was willing to deal with in my living room. I went on the hunt for a filter that was equally as quiet but had a longer overflow lip, and after doing a lot of review reading, I took a chance on a Cascade. The filter is VERY quiet, so that alone makes me happy. The overflow lip is longer than an AquaClear, so it can go longer without being noisy and annoying before I have to top up the tank. So it met both my criteria. I dislike the media that the Cascade comes with itself, and the way it's set up, but thankfully it has a nice sized media box much like an AquaClear, so I just customized it and set it up like I would on an AC and it works perfectly. It does a great job of keeping the tank nice and clear. My only complaint is that in the few months I've been using the filters, I find that they clog and stop running pretty easily. There have been about 4 occasions in the last 6 months that I've discovered the filter not running - when I take it apart and clean out the motor and impeller, it starts back up again. Bit annoying after years of using ACs that basically run forever without clog issues. Overall, a great filter for the price, met the requirements I was looking for, and am happy with it.It's a small little filter that would be perfect for a small nano tank, but mine barely worked so I returned it, even when it did work, it was loud with a lot of air bubbles that would not dissipate, but then it also stopped running a few times within the first 24 hours, unplug it, plug it back in and it would work, but then stop again.The company may have some defective pumps, I am not sure, but having spent this much time trying to get a filter work is simply not worth it, just use a different brand.Cute as a button but mine didn't function reliably at all. I got it for redundancy on my 5 gallon and both my husband and I spent vastly more time trying to get it to run than it spent running. When it ran it was super quiet and the flow was good, ours is just not working. Thankfully Amazon is refunding me, but now I have to get something else for that tank.It seems like most people really like this filter, so I think I probably just got a bad one. Despite this, I would actually recommend it ?Works great on my 3.4 gal. Very small, for some reason I was expecting it to be a little bigger but its cute and works great. The insert is no good. But I left it in for now. I shoved an aquaclear (20/30) bio media bag in it and it just fit. Of course that media goes in a much larger filter so even if I removed half of it. And used filter floss with it. It would work great. For now just the media is working for me and it's quiet with great flow. It says it will work up to 7 gal. An I'm sure it would. But I would only put it on5 gal max myself.