fish gulping for air

[navigator]

hi folks total newbie to this fish keeping hobby, I have a 125 litre tank with 2 clown loaches 10 neons a red tailed shark and 2 black mollies in it, I am now finding that the loaches and also the mollies are at the surface a few times a day as if gulping for air, does anyone know why they are doing this all my water tests are coming up ok.
many thanks
the nav

 

[BettaMomma]

Did you cycle the tank?
How many gallons is 125 litres?

 

[Skylar]

About 33 gallons, BettaMomma. =)

 

[rdd1952]

Are you adding any CO2 to the tank? It definitely sounds as if they are oxygen deprived and are trying to get air. Lower your water level slightly so that the filter creates a little splash when it hits the water. The more surface agitation you get, the more oxygen there will be in the water.

Also, you are overstocked it a 33 gallon tank. The clown loaches alone will get close to a foot long. They need at least a 55 gallon tank. I would try to return them to the LFS for something smaller.