This is a quick and easy DIY Reactor that I threw together mostly with spare parts. I only had to go to the hardware store and spend $2. If you do not already have these parts then it might cost you a couple dollars more. I put this together in minutes and since it is over my sump, I didn't bother to glue the PVC. If this is going to sit outside of your sump you will want to use PVC cement to glue everything together and probably a gasket or o-ring for the end caps.
Drill with 1/2" & 1/8" bits
Dremel or hole saw
1 - 2 foot piece of 2 inch PVC or whatever size you want...
2 - 2 inch PVC couplers
2 - 2 inch PVC end caps
2 - plastic maple syrup taps or appropriate hose connectors
1 - Hose from gravel vac
1 - Maxi-jet 900 or similar pump
Acrylic scrap or about 2 inch by 4 inch piece to make discs.
1. Drill a 1/2 inch hole in the square part of each end cap. This is for the maple syrup taps to enter the reactor. The size of this hole will be different if you something else to connect your hose to the reactor.
2. Cut down the maple syrup taps as shown in the picture below.
3. Glue each maple syrup tap into the hole drilled in the end cap.
4. Unscrew each end cap and measure the diameter of the hole the end cap screws into. This is going to be the same diameter of your acrylic discs.
5. Use a dremel tool or hole saw to cut discs out of your scrap acrylic to fit into the end cap.
6. Use the 1/8" drill bit to drill many holes in the two acrylic discs, this will allow water to flow through the reactor while keeping the media inside.
7. Drop the discs into each end cap and screw back together
8. Put a 2 inch coupler on each of the end caps.
9. Put couplers with end caps on the 2 foot section of PVC.
10. Attach your hose to each maple syrup tap.
11. Attach the output of your pump to one hose.
Unscrew one end cap and remove acrylic disc. Fill the reactor with desired media(Phosphate remover, Nitrate remover, carbon, etc.) and replace acrylic disc and end cap.
I place the pump and output hose in the return chamber of my sump. That way the chaeto gets as much of the nutrients as possible before they get to the reactor.
Here is what it looks like on my sump: