Surface Swimming?

[JustKia]

I noticed over the past few nights that some of my danios swim at the surface in the dark. I had to look closely and it seems a lot of the time that they are at the surface they aren't actually breaking the surface with their mouth - just the top/back of their heads - swimming along (the right way) barely touching the water's surface. When there's a couple at the surface, the others are at all levels in the tank, including the bottom - seems I have a couple of danios who just love being at the lower level and the rest just like to make the most of the whole tank.
* They don't all do it.
* They don't do it at all during the day/light.

I've a fluval 3+ filter with the little extra air intake bit, plenty of ripples/waves on the surface, as well as an air pump that blows fine bubbles through 3 small air stones.
I know fish bobbing at the surface is usually them gasping for air, but that isn't what it looks like, I remember goldfish doing that when I was a kid.
Tank/Water stats here: http/www.fishforums.net/index.php?showtopic=266449

 

[waterdrop]

The danio skimming the surface who finds the insect that drops to the water surface is the danio who might survive! While danios do explore all over the tank, including interesting nosing around stuff at the bottom at times, they seem to be naturally surface minnows in my opinion. Interesting observation about the night/day difference. I might have to set my son watching out for that. He noticed that at night sometimes the fish can seem to disappear in that if you (by accident perhaps) happen to turn the lights on they may have settled in unusual places and may be quite hidden in the plants and decorations. First night after he got his new shoal of neons, he thought they had disappeared like this.

~~waterdrop~~

 

[Jallen]

Some of my tiger barbs do this. It's not a bad thing. The tiger barbs are at least 4 months old now with no problems. Fairly sure it's because they can't see properly.

 

[Davo86]

all of my Giant Danios do this late in the evening, they swim against the current in the direction of the filter outlet, presumably catching any food particles being blown towards them.

 

[JustKia]

OK just being over cautious then =)
And yes, they also swim towards the filter flow (against the current), occassionally letting themselves be swept along by it instead.
Oh the joys of observing little creatures up close =)