Can I Add "flow" To My 30l Tank?

Hi guys

I bought my first tank this year and have read loads about fish liking to swim against currents. I bought a 30L tank as a starter and have 2 mollies and 4 neon tetras. I want their environment to be as good as possible ( I have added a heater and an LED light bar). See picture attached.

I want to add some horizontal flow rather than just the vertical air tube thing from the air filter that came with it..

If I bought another small air filter and just ran the air tube in and put it over one side pointing sideways, do you think that would work? Any other ideas? I could attach an "air curtain" to one side of the tank (in an upright orientation) that might push air around maybe? I don't want my tank full of bubbles though so - just for something for the fish to swim against.

Can't be too big either due to small tank!

Any suggestions?

Thanks

what filter have u got ?

Standard BiOrb filter currently. Airpump pumps air through a spongy filter in the tank and bubbles upwards. (as in pic in the very middle). Was thinking about buying a cheap second pump and running an air hose into tank specifically to create a "current"...

what shape is the tank - hard to tell from pic

Approx measurements are:

Height: 45cm
Width: 40cm
Depth: 30cm

Total capacity is 30 litres

i'd get a small internal filter with a spray bar
i got one on my 60l tank and was only about £10
ebay - 180910282269 - thats what i got

Thanks for responses Fish Fanatic. I'll have a look at at a small cheap spray bar and a small air pump and see how they get on with it!

cheers
M