How to hide an internal filter in an aquarium?
Nobody usually likes visible technology in the aquarium, but without technology it is (almost) impossible.
The technology can be covered with roots or stone structures. However, make sure that the flow through the filter is not blocked.
In a well-planted aquarium, the green filters or pipes disappear.
If you have a black filter, you can also attach a black film to the back (outside) of the aquarium so that the filter is no longer noticeable.