Ok I dont see anyone mentioning this trick so I'll post it.
I have those hang on the side/back overflow filters, a common style. the one I have now is a AquaTech 40.
These take a special filter cartridge that I can only find with charcoal, and dont normally need or want charcoal all the time. Plus, these things get expensive since the clog up a few times a week, and are a pain to wash out.
I have something better.
To do this I use the cages from large size Topfin filters, but these are the same as some tetra brand filters too. I imagine they will fit other models I've never had to.
Point being, you need to be able to wash the thing out well enough to be "as good as new" again and not cost you 15 bucks for a 6 pack.
The solution is pantyhose.
Depending on how fine you want to filter, you can get pretty thick mesh, or very thin sheer mesh. My chick buys all kinds so I have a can full of (so she says) worn out pantyhose. They get a run in one spot and she tosses them out.
I like the very sheer mesh, because it can filter fine or not so fine.
In the pics, you see new filter #3 out of the box. These wrk well for a while, you can pull the bag off and wash it out, but they never wash out like new again.
when the bag is removed you have the inner cage thing, (#1) and all you need to do is cut a piece of the pantyhose leg off, and tie a knot in one end (unless you have an intact toe section then you can forgo one knot) and slip it over the cage, then tie a knot in the top.
Presto, you have a new, super easy to flush clean, free new filter cartridge that will filter out much finer crud than the original white floss bag. Plus it fits right in the filter housing and under the lid so no one knows you are being a cheapskate.
OK now, depending on HOW fine you want, all you need to do is either leave the nylon mesh loose, or, stretch it as tight as you like, since the tighter you stretch it, the larger the particles it will let go through it.
Once my water is nice and clear, I keep the mesh on the cage pretty tight, and it does a fine job of filtering out really fine crud from the water.
Yes, this will clog up faster than a white floss bag, BUT they clean out alot faster and MUCH cleaner.
Hit the outflow side with a sink sprayer or the like, and the mesh flushes CLEAN. No fighting with the white mesh to scrub n rub the fish crud out (and never getting it all). The nylon flushes clean quick and easy, you don't even have to get your hands wet.
yes, after a few dozen flushes the mesh does start to get hard to flush out as bacteria grows on it.
No sweat, one pair of your wife's discarded pantyhose will make you a dozen brand new filters.
Go buy her some flowers. She will save you a bundle on fish filter cartridges.
If someone else posted this idea here and I missed it.... oh well here it is again.
Also, now and then you stir up the tank and its a muddy mess, if you have a powerhead, if you make a 12" bag from a section of nylon, and bag the outflow nozzle, and turn the flow rate down, you'll be amazed at how fast the water clears up, to the point the normal filter box will finish it up without the fliter getting clogged 15 times that day.
For that, you will want to use the type of hose that is really thick and heavy.
Ugly yes, but its a temporary clean up filter you will only use for a day.
I'm sure there are other styles of filters that the pantyhose refit would work just as well with.