I have a 20 gallon tank that's been established for maybe 8 years or so. It currently houses some platys (fry to adults), two minnows, and nine amano shrimp. I do regular water changes, and in general have a healthy tank. I've replaced the heater twice, and the lights once or twice. Attached to the tank are two filters, one biowheel and one whisper power filter (not sure the model). However, nowadays I find that the whisper power filter doesn't have good flow anymore. It seems to be due to algae buildup within the innards. If I clean out the filter and the impeller, the flow improves, but it eventually goes bad again, with increasing frequency. I can't open up the tubing/innards to clean out the algae, and I'm guessing it's gunking up the works. Or maybe the motor is going? Is it time to get another HOB filter? I have two of different types in case one conks out.