
In an ideal world the set up you should be focusing on is this as with all filtration.We need to separate the solids fro the water column.By doing this we can keep our culture of bacteria in top form breaking down dissolved waste.Unfortunately this is seldom achieved most filters will turn into a big mushy nightmare if not maintained properly.So when choosing media it is more a personal choice.When it comes to multibay filtration for koi etc nothing beats filter brushes in the first chamber as long as the chamber is sized correctly.You can put all the modern gadgets against this old technology and i haven’t seen it be4ttered yet but the hobby is all about selling gadgets so let them at it. I come from a thinking approach fish have been my life for over 30 years we used to make professional filters ad on occasion we still do when we need too.Brushes will settle solids and solids stick to solids so with in no time you will be shocked at the amount of physical waste a couple of brush chambers in inline will collect.Anyway for a sump we are more restricted.The biggest problem is the return from the tank which will be approx 3500 lph.I do suggest the sock great idea to a degree but the solids will eventually go into solution you will only trap the coarse material but it is something i like the concept…..like all concept.You need to provide a way of slowing the water to a halt so solids will precipitate out of the water column.Bio balls are as good as any but layers of poly wool would be more effective.I love poly wool it is so versatile.It ticks all the boxes.You can use it to prestrain and trap the solids keeping them from moving through the system.Remember to turn off the sytem before removing so you have a static body of water.This prevents contamination of other chambers then you can syphon off the solids that settle while you do your maintenance.Biological media i love siporax it is tremendous every copies it in one way or another but the original is still the best.Sera do bulk siporax we are the agents(little plug there).As a guideline it takes about a cubic foot of media t handle a 1000 litres of water you can use that to gauge the project.I would then use my graded foam coarse medium then fine on the return pump just to keep the last escapees from beating the system.It does not have to be complicated.Fish keepers ultimately battle with particles……its all a visual thing……particles will be beaten by flow rates and the correct building of the weir in the tank.If your weir is just a standard over the top job you will have problems if it has an outer box that collects from the bottom first then you are ok i guess.You can always use an external for removing any stubborn particles in my opinion.
Remember overcrowd your africans this is the way they exist in nature maybe stick a giraffe cat in with them to stir up the sand they are brilliant for hoovering tanks.So i hope this has been helpful to you.
Best of luck
Ian