I've just ordered my new tank, 7.5 x 3 x 2.5 for rays and having a custom built glass 4 x 2 x 2 tank for a fluidised bed.
Ye I think I'm going to go for a tank instead of barrels, what air pump are you going to run ? I'm thinking of getting a 100l per min would that be enough do run the sump and a few air stones ?
It has a settlement chamber first, then sponges, and then area to hold the media, then a section for a return.
It's basically the design of the king of diy one on YouTube, ( the new design for acrylic tank, not the barrel design) but with a settlement chamber first to catch most of the huge rays poop and save cleaning sponges as often lol