Size: Large 12 Pack
First: People want to know what the actual size of these are so they can decide if they'll fit their filter. I got these to use with a Tetra Whisper 30-60 that I got at WalMart. They're exactly the right size for this filter (and certain others, of course).
Measuring the bags or the frame over which you place the bags gives, of course different dimensions. But here's what I get measuring a brand new bag stretched over the frame at the very outside edges of the bag: The frame and bags are tapered so that they're narrower at the bottom and get wider towards the top. That allows them to be inserted into the filter more easily yet still fit in tight enough to make it hard for the water to short circuit around the bag.
At the top, measuring to the very outermost reaches of an unused bag, I get a width of almost exactly 5". At the bottom, where it's narrower, measuring the very outermost edges of an unused bag, I get a little under 4 3/4". The height, again, measuring from the very bottom of the edge of the bag to the top of the frame (which sticks out above the top of the bag, of course), I get a height of just about exactly 7".
Naturally, the bag's edges get smashed inward a bit, its edges curling up and mooshing in as you slide it down into the slot for it in the filter. So measuring a used, wet, bag will give you slightly smaller dimensions. It might actually be of more use to people to know the dimensions of the frame since that's what has to match and fit exactly into your filter, and you can measure your existing bag frame to see if it'll be the same.
The frame I got with these "Large" bags is about 6 3/8" tall, 4 5/8" wide at the very top, and about 4 1/4" wide at the bottom. I'd compare those dimensions with the existing frame from one of your filter bag assemblies to decide if these "Large" bags will fit your particular filter.
I cannot comment on the sizes of the medium or extra large bags. Again, the ones I got are the "Large" size.
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Now for the review:
Based on use with my Tetra Whisper 30-60, these work just the same as the pre-assembled units, but cost a lot less. Once assembled, they're exactly the same as what come with the filter.
The amount of activated carbon supplied for each bag in these kits is the same as the amount that comes in the pre-assembled elements. I personally don't think it's enough, so I like to add more (about three times as much as what is supplied) when I make up or clean mine. That means obtaining similar granular activated carbon elsewhere, of course.
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A bit of advice for people new to all of this:
One thing that's important to keep in mind with any aquarium filter is that along with mechanical filtration (to get out obvious debris) and chemical filtration (the activated carbon), the main function of most aquarium filters is the biological filtration provided by the so-called "beneficial bacteria" which hopefully colonize your filter elements.
The basic idea of this biofiltration is that two types of bacteria will eventually colonize the surfaces in your aquarium and especially your filter media. One type of bacteria "eats" the ammonia excreted by your fish, and, as their waste product, excrete nitrite. The second type of bacteria "eats" nitrite, and, as their waste product, excrete nitrate.
Ammonia is highly toxic to fish even at fairly low concentrations (depending on pH to a great degree). Nitrite is also quite toxic to fish. Nitrate (the end result of all of this bacterial action) can be harmful to fish at high enough concentrations, but is not nearly as bad as the ammonia (produced by the fish) and the nitrite (produced by the first type of bacteria mentioned).
So once your aquarium and filter system have established colonies of beneficial bacteria large enough to metabolize the amount of ammonia produced by your fish, the main things that harm fish in a closed system (like an aquarium) will be kept in control. However, the nitrates will still build up over time, and this is why we need to do periodic water changes on our aquariums. People do water changes every week or two, generally.
But without sufficient bacterial colonies, the ammonia produced by the fish would kill them in very short order. You'd need to do almost constant water changes to keep the fish healthy.
So the main point I want to make is this:
If you remove and replace, or clean too thoroughly, your filter media, then you will be discarding much of your beneficial bacteria. This can kill your fish. To learn more about this, read up about the "Nitrogen Cycle" for an aquarium.
So with a filter like the Whisper 30-60 that has two identical sets of filter elements, I prefer to avoid replacing the filter bags until they're absolutely falling apart. Instead, I rinse them out in used aquarium water and replace the activated carbon when doing a water change. This preserves the bacteria colonies in them and avoids shocking the tank by removing too much of its beneficial bacteria all at once, destroying the balance.
Remember: You need to have enough bacteria present to handle the amount of ammonia produced by your fish (and rotting food from overfeeding), etc. Over time, the bacteria colonies grow to match the amount of ammonia being produce by your fish and your excess feeding. But there isn't a lot of excess bacteria because if there were, some of them would starve off due to a lack of ammonia. So the bacteria tends to stay in balance with your fish "load".
If you suddenly remove a large percentage of the bacteria present in the tank and filter(s), then, until the bacteria can reproduce and the colonies grow back, there will likely be an excess of ammonia, and this can kill or injure your fish quite rapidly. So you want to protect your bacteria so it can protect your fish.
I never do much of anything to the open-cell foam elements. They're meant to house a lot of beneficial bacteria, and cleaning them off will just remove that needed bacterial slime (biofilm). You don't want them to plug off, of course, but if you've maintained the bag filters ahead of them, then nothing should reach these foam elements to clog them up, anyhow. If they do plug, though, then I recommend rinsing them gently in used aquarium water, and not trying to get them too clean. Remember: You WANT that slime of biofilm to remain since that's your necessary bacteria colonies! The thin slime layer is good. :)
When I do need to actually replace one of the filter bags, I only do one side of the filter at a time, waiting a month or more before replacing the other side. That way, hopefully the first bag that was replaced will have built up enough of a bacteria colony to handle a lot of the load before I dispose of the other one.
Some of these filters are smaller and only have one bag and one foam element. In that case, you want to be especially careful not to clean the foam element if possible. And ideally, don't replace the filter bag any more often than you have to. Again, just rinse it out in used aquarium water to restore good flow, and replace the activated carbon when you're doing a cleaning.
When you DO have to replace the filter bag (they last about a year for me) you may want to rinse what's left of the old bag, and then put it into your filter right behind the fresh new one. Then leave it in there for a month or so to provide its bacterial help while the new bag gets seeded from it (the old one), and finally establishes its own new colonies of bacteria.
I like to have several filters in each tank. That provides a "backup" location for bacterial colonies to help handle the load when you do have to clean or replace a filter or have a failure of some type.
There are some great on-line forums for fish keeping where you can ask questions and learn more about all of this.
Beas
KC Reviews