Tetra Whisper Bio-Bag Filter Cartridges for Aquariums, Medium Filter for Freshwater and Marine Fish, Removes Odors and Discoloration, Easy to Assemble, 6 Medium Green Filters

We have two Tetra Whisper fish filters. These assemble-yourself filter cartridges or "bags" are, after assembly, the same as the ones you can buy ready to use but much, much cheaper. It is extremely easy to assemble them and everything you need is included, very nice and I think a "no brainer". NOTE: I recommend not following their assembly instructions in one respect. ("Assembly" means turning off the filter unit, removing the old, dirty cartridge to work on it, changing out the filter bag and charcoal [ditch the old, put in the new], and re-installing.) The instructions say to put the re-useable frame inside the bag first, then pour in the charcoal. I find that no matter how careful I am, some of the little charcoal particles spill out of the narrow opening or bounce off the frame as you pour and they wind up, (a.) not in the filter so less service life, and, (b.) on the floor or counter to be cleaned up. Instead, I recommend pouring the charcoal into the bag first with the bag "mouth" wide open and unobstructed, much easier and less mess and waste, then insert the frame into the bag. The only caveat is that with the charcoal in a pile at the bottom of the bag, the frame may not go down in all the way, so have to shake or flick the bag a bit then settle the frame in deeper once or twice, much as you might flick a single-serve paper bag of sugar to move sugar out of the way before tearing off the top. I haven't "autopsied" a factory-assembled bag vs one of these to confirm that they aren't cheating by putting in less charcoal, the price difference is so great that it's surprising, but they seem to work for as long as the factor-assembled ones. The box says "Made in U.S.A." so I hope we're not putting someone out of work by taking away their factory assembly job, but I'm sure the factory-assemble versions remain a major part of the market. We keep a few factory-assembled ones around for when we are away and the pet sitter may have to change cartridges, not they couldn't use these (not rocket science!) but we try to make it easier for them. For us, we use only these unassembled ones. The Whisper filters seem effective and are quiet. They do build up some crud over time and should be rinsed out once in a while, including taking off the bottom section (intake screen and pump), but other than that they seem good. Of course, the local pet store fish experts, who do seem to know their stuff, say that sometimes cleaning is good and eliminates crud that otherwise makes the water cloudy and the fish prone to infection, while other times cleaning removes "good" slime and organic material that are necessary to support or are part of the "good" bacteria that should be present in an aquarium to digest and remove ammonia and nitrates (i.e., piss-eating bacteria), since not having them results in impurity build-up in the water than can irritate, hurt, or ultimately kills the fish. But no one has been able to tell me how to tell good slime or crud from bad slime and crud beyond saying that if the tank water looks clear, don't sweat the slime, but if cloudy, that's bad. They also say to add "biological" treatments or additives when appropriate to establish or restore lost good bacteria, but then add that the "good" bacteria under some conditions can also make water cloudy and bad. Confused yet? So am I. At this point, I should say that I like hamsters and cats and dogs myself, but we have the fish for the kids (sigh) and we do the best we can. So if you have fish and this type of water filter, I would recommend these unassembled ones, they are sooo much less expensive than factory assembled, easy and very little trouble to assemble yourself, so you can save money and/or change filters cartridges more often. It's all good.

Classic brand works well.

Easy to put together and works

These definitely don't hold up as well as the premade ones, but for the price I'm willing to change the filter out more often.

Good value pack lasts for at least 1 year

These are so easy to use and at a fraction of the price! I love these, as they are quick to make and work just as intended as ones already together. Easy to clean, lasts a long time! Works great filtering the tank!! Easy assembly!!

Great filters and excellent deal

Fast shipping fair prices good items