There are many types of filters which have been used in small quantities in some aquariums by some folks. I’ll review them in these chapters:
Note this is far from an exhaustive list. There are all sorts of filters constantly coming and going on the market. I can’t keep up with them all. For instance there is a type of high performance filter is called a bead filter. It is a fluidized bed filter which uses small plastic beads. Properly set up and maintained these are two to three times better than K1 fluidized beds. But they are very difficult to operate and maintain.
One great idea for an inexpensive high-performance filter for a large aquarium is to buy a low-cost sand filter designed to filter pools. Instead of sand fill the filter with K1 type media. Rachel O’Leary came up with this brilliant idea. The filter will require an external pump.
Another filter which is excellent for large aquariums is a pond canister filter. There are some inexpensive pond canister filters which have close to a cubic foot of foam in them. These filters need a pump added (they generally use an external pump suctioning the canister) but they are a very inexpensive biofiltration option which can biofilter roughly seven pounds of fish each.