I bought 3 of them plus one of the 12 inch long air stones .The 12 inch one has to lay flat and you cannot drop it more than 6 inches .The airballs I have them high now until they absorb more water and then I will drop them lower .But for 1.49 that is a great price .I rated them on there sight and got vip points too for my next purchase .They have them listed under fish not under the pond stuff .I didn't want to change the pond much because what I had going was working great .But still worried about that dog .I was out mowing and trimming friday and there under my pear tree was fresh dog doo .Not sure but must have been what King Arthur was barking at the other night and last night too .I thought he was just barking at a deer .I could not see anything .My dogs are fenced in so know it was not them ,they can't get to the pear tree.I will have to go see the new people and see if there dog was loose again .It was not near my pond that I can tell.Yeh and they are on the pump with 3/16 th air line that I got on e-bay .They work great