I made it.
Its a old pool filter. 1 inch inlet and output. Theres a pump fitted inside the filter. Just a pond pump sort of things. Media is pumice and 2 grades of filter wool.
Knife and datnoid died in the tank for some unknown reason. A new datnoid has replaced them.
Bichirs are here next to me, trying to get the to spawn.
Also hoplos have been added.