I use to have the tiles directly on the ground but when I got frags in and wasn’t ready to mount them to the tiles I would have no where to put them as I didn’t have a frag rack. I ended up adding eggcrate to lift everything off the ground an inch, which now allows me to stick a frag plug in it.
What I did was cut little 2” squares of eggcrate, stacked them on top of each other and placed them all around to hold up the main eggcrate. Not the best pic but you can see the eggcrate stacked and also see the frag plug to the left that’s now able to go into the eggcrate.
For flow I use two of the maxspect gyre 250’s. I put one on each end of the tank and offset them a little from each other to make sure the whole tank gets good flow. I run them at about 40% in alternating gyre mode.