Whisper^® Internal Power Filter

Typically, about every three weeks, unless you are heavily stocked or feeding too much. Brex

That filter is operated by an air pump. You should hear a quiet hum from the pump if you are next to it, and some slight bubbling sounds from the filter. Make sure the water level in the tank covers the filter spillway. If it appears to be struggling, check the hole in the bottom of the filter body where the tube attaches to it and make sure it is not clogged. Brex

It will work in one, yes, but not well. It's not large enough to do a thorough job of cleaning. You could use it as a supplemental one or temporary one. Brex

That depends on which one of these internal filters you own. The 3i and 4i take the Xsmall. The 10i takes the medium size, and the 40i takes the large cartridge. Brex

That depends on which filter you are referring to - we have several sizes of internal filter systems.The one pictured takes the Size Small Bio Bag. Brex

No, this filter is 120V and 60 Hz. Brex

Hi Laurie, It's normal to get green algae in a tank. The best way to control it is to vacuum the gravel and change about 25% of the water once a week in such a small tank. Larger tanks can go longer. After you remove some water, you use an algae pad to clean the algae off of the glass. Typically the first 3-4 months of a tank's life is when algae grows the most and it will come under control with regular water changes. In older tanks, it becomes an issue due to overfeeding, lack of water changes, too much or the wrong type of light, and sometimes the tap water being used is an issue. You should not need an air pump, no. Some live plants may help if you are already doing water changes, and only have one or two very small fish that are not goldfish. Brex

You should have the new Whisper 4i filter which is motorized. The pump snaps onto the bottom of the filter body, and yes, the entire thing goes down into the water. BREX