Trouble with flow after Cetus

[Mohawk]

Plumbing question. I am having trouble. Pond is gravity fed to Cetus via bottom drain. Bottom drain is unobstructed
and has been snaked to make sure. Flow appears very good TO the Cetus. The issue appears to be FROM the Cetus to the waterfall.
I have tried 2 different pumps (sequence 750 series 4200seq12 and sequence 5000 seq 20). I made the modification tot he Cetus
to enlarge the exit from 1.5 to 2 inches. With the smaller pump it goes fine for a while then will not keep up with the Cetus and it fills up
above the screen. With the larger pump it will keep up but after an hour or so it will have no outflow as if air was getting into the line.

I know this is a lot but if you could look at my pictures to see if something obvious is missing or any other things to try. I have used a ball balve
after the pump with no luck.

Justin

 

[poconojoe]

What is a cetus?

 

[poconojoe]

Not sure what your problem is, but I remember reading something about when pipes are run high over a wall, air can get trapped in the high part. I vaguely remember reading something about drilling a small hole somewhere in the pipe to prevent this. Not sure where to locate such a hole.
If this is your problem, hopefully someone more knowledgeable here will help out.

 

[mgmine]

I'm not sure what a cetus is either. But you say that the bottom drain is feeding it via gravity. In order for gravity to work the cetus has to be lower than the bottom drain. Water will seek its own level. Can you explain more about where the pipes are going to? Is the gray box a filter or is it the cetus? Is that the pond that the box is sitting in? Where is your pump located and where is it pumping to? The pipe laying on the top seems to be going nowhere.

 

[poconojoe]

Still no explanation what a cetus is!
I looked it up. It's a constellation, an ancient sea monster, probably a whale.

 

[mrsclem]

Sieve filter