well when i first put it in i had no problem but after a few months and the tank got a bit of slim around the tubes one side was blowing bubbles fine but the other side was blowing bubbles up the tube but only coming out the top like this ,,,,,,,,, ,,,,,,,,,,,,, ,,,,,,,,,,,,,,, ,,,,,,,,,,, ,,,,,,,,,,,
if you understand that... then eventually it stopped and now the other one is doing the same thing... yesterday i bought an internal filter for the tank... but still would like the air pump going aswell...