filter questions

[scott764]

Hi, Im new to this and have an Aquaone At-882 filter. The water needs to be to the maximum line on the filter or it just blows bubbles and even then it still puffs out bubbles every so often. Can someone suggest why it does this and how I can fix it?

 

[RMPD109]

What type of filter is this(canister, HOB). If it is a canister type then it is pulling air from somewhere. If it is the HOB type then the water is being agitated somehow and returning to the tank.