It's actually the reverse. Incoming pipe is low and outgoing pipe is high. Reason being is that when the dirty water comes in with the fish waste, the solids will settle (as they are heavier), so they will sink. And the clean (lighter) water will rise up. So reverse your pipes.
Also, in your incoming pipes, put two 90 degree ell (or sweep) elbows on it so that you start to create a "venturi" effect. In otherwords, the water starts to swirl in a circle so that the settling stuff/crap stays down. The black buklhead on the top is where my outflow pipe is.
Here's a pic of mine to give you an example:
Let me know if this doesn't make sense to you. But crap sinks, clean water floats. Then when you flush your drain at the bottom of the barrel, the crap will easily come out. This is called an "upflow" design. There are also downflow designs (like your pic), but they are not as efficient.
Also, in your incoming pipes, put two 90 degree ell (or sweep) elbows on it so that you start to create a "venturi" effect. In otherwords, the water starts to swirl in a circle so that the settling stuff/crap stays down. The black buklhead on the top is where my outflow pipe is.
Here's a pic of mine to give you an example:
Let me know if this doesn't make sense to you. But crap sinks, clean water floats. Then when you flush your drain at the bottom of the barrel, the crap will easily come out. This is called an "upflow" design. There are also downflow designs (like your pic), but they are not as efficient.