waterdrop
Enthusiastic "Re-Beginner"
LatLine, Interesting, I remember moving my skinny siphon tube around the gravel trying to get dirt, never thinking how clever it would be if combined with a wider tube like my hand-pump gravel cleaner had. I'm sure the hand-pump type which simply returned the filtered water to the aquarium seemed more attractive back in those days because I had little idea how important water changes were. The cloth bag hand-pump(or battery) things were only as good as the cloth bag, which was only good for larger debris mostly.I remember those. Never had one as I always did gravel cleaning when doing a water change so used a wide ugf uplift tube connected via a bored cork to my syphon tube thus the crud was straight out of the tank at the same time as the water.But the gravel cleaner was one of those ones where you squeeze the suction bulb at the top and it just pulls the water up the stiff plastic tube and dumps it over into a cloth strainer bag.
I used ugf's from the mid '60's until perhaps the mid '80's by which time I had changed over to external canisters on all of my tanks, (apart from fry tanks of course - sponges).
The betta comment above is also good, betta's like a fairly still surface environment.
I wonder, you being in Denmark, how you came to know that water changes were good? Some here in US say that the fellow Innes who had the most popular large aquarium ref-style book of the time was one who went against the grain of "old-water-is-good" dogma but I was probably too young to see that subtlety in his recommendations.
Regards, ~~waterdrop~~