Just to clarify....
You don't need to "prefilter" the water before the PUMP - at the pump inlet. What you need to do is prefilter the water prior to introducing it to your bio-filter.
You just don't want to send all the "muck" into the bio-filter because even small bits of scum and muck can clog the the bacteria cultures.
The water will flow through your media just fine, but too much fine debris, detritus and "fish poop" can hamper the microscopic colonies of bacteria living on your media.
You can send the output of your pump through a mechanical filter or a mechanical "separator" to reduce all that gunk before it gets to your bio-filter.
You do NOT need to prefilter it ahead of your Tsunami pump for this specific purpose, but it would be better if you could place your pump after the filtration system if possible.
I will explain that more in a moment.
A sieve filter or a radial flow filter are two really swell options which can be fabricated very inexpensively and without too much engineering - especially the radial flow.
But, there are other means that you could investigate as well, such as a vortex separator or a large settling tank. These latter two options require a LOT of space and a BIG tank.
If it were at all possible to feed your dirty pond water to your filter system via gravity flow, then any muck that goes through the system won't be minced and pureed by the impeller of your pump.
This makes it MUCH easier to separate the muck from the water because all the muck will be of larger particle size and thus heavier and precipitate / separate more readily. When you put the pump in between the pond and the filter system, you dice up the muck and make it more difficult to separate.
Hope that makes sense and you can determine a method to apply it.