This working prototype I built in about an hour and so far it runs very well but I didn’t put the diatom powder in yet.
The main two parts are a typical under sink water filter housing available from Amazon for about $20.00. The pleated filter cartridge inside is a 30 micron. They sell a one micron and if you use that you don’t need diatom powder but I want to try this one first with the powder.

The pump is a 500GPH Supreme Hydro-Mag pump. $68.00 on Amazon

The membrane inside is $13.00​

Pentair Pentek R30 Sediment Water Filter, 10-Inch, Under Sink Pleated Polyester Filter Cartridge, 10″ x 2.5″, 30 Micron​

This is the finished prototype ready for testing.

The galvanized cap on the bottom of the filter is a 4″ end cap for a dryer vent duct. It will corrode so I will replace it on the finished model with a rubber one available in a plumbing supply of Home Depot.

I also would not use that piece of “melamine” shelving material at the bottom as it doesn’t do well with water. I will use either Plexiglass or varnished wood.

I also will replace that clear tube between the pump and filter with a 1/2″ PVC pipe using a union in the middle for ease in taking the thing apart.

But it is working perfectly and I couldn’t be happier