Problem with marineland filter overflowing

[Voodoodol]

Yesterday I topped off my thirty gallon like I do every day. A few hours later I notice that the water line is far below where it should be. I start looking for cracks but, thankfully, find none. I finally notice that the water is coming from the filter. It's a Marineland Penguin 300 that I've been using for a few months with no problems whatsoever. It has started flooding. Water just doesn't stop where it is supposed to and runs right over the back and sides. I can't figure out why it's flooding or how to stop it. Nothing has changed recently except I added a protein skimmer last week. I can't see how that would cause it.

 

Any ideas or advice would be greatly appreciated.

[Chadf]

Are the cartridges clogged up or wheels not spinning freely?

 

Also, if it's on a rimless tank make sure it isn't hanging off the back making it unlevel.

[Voodoodol]

Cartridges were replaced last week and look fine. Wheels are spinning freely. My tank isnt rimless. The filter does hang off the back but it's level. I will take it off tomorrow when I get home from work and see if tinkering with it will fix the problem. There is additional filtration on the tank so no worries there.

[JanB]

Just got the Marineland filter. I have 3 very large goldfish( rescued them as babies from pet stores last year.)They have now spent 2 summers in large outside containers. They stay in the basement for the winter with a light over the tank. I have tried several filters. Wanted this as a backup. Not impressed. Went to feed them just now. Filter had overflowed and soaked the carpet. Unplugged and took everything apart. Biowheel again not turning. Cleaned everything. Only had this about 2 weeks. 4th time to do this. Getting sick of cleaning up a flood. Yes. The filter is level.