What I don't quite understand yet why the thread without mentioning in original post that it was for a 1.5 gal tank. Unless this is supposed to be a reply that accidentally got posted as new thread?
Good point, Duckie. I should have given more background on the original post. One of our members was saying in chat that his desktop 1.5 gallon plant only tank was not as clear as he'd like and since he didn't have any fauna in the tank, it was unfiltered. He also stated that he had a small air pump and was trying to come up with some ideas for clarifying the water. A corner box filter would have been too big for the tank so I thought something like the drawing might work. It's only functions are to mechanically filter the water slowly and give the tank some movement and better oxygenation to keep the tank water from stagnating. That is floss at the bottom of the tube, not a sponge.
If it doesn't work, other options can be pursued. The member had all the parts to make the little filter already so he's out of pocket nothing.
I'll see if I can get him to post whether it's successful or not.
Again, the picture is turned 90 degrees. The tube should be vertical to work properly.
I have a mini filter from years ago when I started in the hobby. It was is or was an Art Deco hob filter. It's for tanks that are about 2 gallons. I think I still have it. Nice little filter for a tiny tank.