Every once in a while one of my tanks will seem like it has some extra particulate matter floating around. This can be the product of many things - new rocks or decorations - that weren't adequately cleaned before adding them to the tank. Or sometimes the filter you're using just needs to be cleaned more frequently because you've increased the bioload or added some new cichlids that keep the substrate stirred up more than usual.
Also, for the sake of redundancy, a little extra water movement isn't a bad thing, unless you have lot of plants (but that's a post for another day). If you follow the blog regularly, you know how I feel about redundancy.
So how can you clear up particulate matter while simultaneously increasing the bio-filtration and moving some extra water at the same time? The easy answer is to add another filter. No problem, if you have an unlimited budget and the time to set one up. However, you might just have what you need to accomplish both goals without leaving your house.
Do you have a powerhead that you aren't using or a small submersible pump? How about a 16 oz. plastic water/soda bottle? What about a power drill? There are several YouTube videos available that show you how to create small internal filters using plastic bottles and powerheads. Check those out. You can even make these bottle filters with air pumps, but I only use air pumps for power outage emergencies.
I posted a couple of years ago about my own filter design that I borrowed and customized from those YouTube videos. Instead of soda bottles, I use condiment squeeze bottles because they have wide mouths. As a result, I can easily get media in and out but I can also secure whatever I use in the bottle because of the screw on tops. You can pick up two or three of these bottles online for just a few dollars. I also like condiment bottles because they're generally larger in volume (24 oz or even 36), which allows me greater versatility. I can apply new mechanical and biological filtration simultaneously without taking up a great deal of space in the tank while moving more water at the same time. You can also use small submersible pumps instead of powerheads, if you prefer.
In the photos below, you can see a small (16 oz) condiment bottle with a powerhead. I drill small holes in the lid of the bottle (photo 5) and one large hole in the bottom of the bottle (photo 2). The large hole in the bottom is where the bottle attaches to the powerhead or the pump. You can fill the bottle with polyfill (not pictured) for water polishing (removing fine particulate matter) or you can use your favorite bio-media for extra biological filtration. You can put the media in loose or use a media bag (photos 3 and 4). When I use these bottle filters for extra biological filtration, I insert a cut-to-fit sponge in the very top to also provide a little mechanical filtration (not pictured).
What's the advantage of this DIY internal filter over a new store filter? Cost, aesthetics, and flexibility. Building this filter with a small powerhead can be cheaper than a retail filter. It's easy and quick to set up as opposed to a new canister filter or sump. It's easy to hide behind some rocks, which you can't do with a HOB filter. Lastly, you can vary the size and type of media you use by swapping different size bottles. Furthermore, I can move the whole filter unit around pretty much anywhere, change its intake depth, modify the outflow direction, and change the media at will using whatever I want.
Remember the purpose of this is multiple - remove particulate (water polishing), provide extra biological filtration, and provide extra water movement.
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub