here is most of what i used to build the reactor the eheim pump was the most expensive thing in the reactor at 34 the soda bottle was free from my post 77838 0 04510400 1357229507 thumb jpeg post 82694 0 52678800 1387906705 thumb jpg cut some 5 8 vinyl tubing roughly double the powerhead s worth at this point you should also reem out the neck of the bottle where the cap img d d fmr75 kit fluidised reactor pump suitable rowaphos sand bio pellets pearls biopellets in use un the union and rest the pipe somewhere off to the side use a funnel to fill with biopellets now just shove the bottle onto the vinyl tubing upside down post 77838 0 44771500 1357229232 thumb jpeg img after the superglue cures glob on some pvc cement and slip on the threaded end of the 3 4 union after the union is on i used a q tip to dab some pvc post 77838 0 16676200 1357229519 thumb jpg the end cap was glued into the opposite end and was drilled with a 7 8 paddle bit to accommodate the flexible tubing coming from the nextreef reactor but first i had to understand what a biopellet was and how it worked to lower nitrate and phosp in my system my layman s understanding is that the the piece fits over the intake to the eheim pump and the cap drilled out in the forefront accommodates the flexible 5 8 tubing the output of the reactor goes into this fitting that i fabricated with a tee fitting and cap has any used the reactor externally i just bought mine and started modding it the pump looks like it will pop the seal once it has pressure behind it an average days worth of effluent after the bacteria began to colonize in big numbers 20170807 185652 jpg here are the photos of my v1 reactor on image to zoom v2 bio react 500 multi purpose aquarium filter reactor on image to zoom my experience with biopellets d d fmr75 kit fluidised reactor pump suitable rowaphos sand bio pellets pearls