Thank you Bas. Good points.
I am mulling over an experiment where I could pull off outfitting the 10K gal (18ft x 16ft x 5.5ft) with biofiltration in-situ, no separate filter, toward which purpose I'd need to provide a lot of surface area inside the 10K (need robust materials at the same time too) and good stirring for high oxygenation.
The turf would not be on the bottom, I'd not want for detritus to accumulate in or under the turf and then having to vacuum. I don't vacuum any of our tanks. I vacuum our 4 sump filters only once in 1-2 years. Except for the 25K, which has a mat on top of the shower tower filter that needs regular vacuuming. Even that got very old, I'd rather wallow in fish feces and vacuum a sump for one day in 1-2 years than vacuum this shower tower mat every 1-3 days. In other words, it might be nice to hook up the 25K to the 15K sump, the option I decided to pass on, back when I worked on the 25K.
I'd still need to remove the accumulating waste from the 10K and plan to arrange the current such that the waste collects in one spot, where a pump can be placed so that the waste could be filtered out and the water would get well oxygenated and returned to the tank.
On the bare bottom it is planned to have about 100 big boulders, about 1.5-2ft in diameter, not round but approx. This is for looks, additional surface area (the surface of the boulders is somewhat porous), and perhaps for small fish to avoid big predators.
I am mulling to try to have smaller frequently-breeding fish in the tank for large predators and to have safe(r) places for them to hide away and to breed / grow up. Toward that some artificial fish habitats can be home-built or purchased, e.g.:
https://www.thepondguy.com/product/porc ... es-3-pack/
https://www.thepondguy.com/product/pond ... ole-brush/
, to which I might attach the turf, as well as strips of turf can be hung here and there hanging from the tank's cover, like so
https://www.thepondguy.com/product/pond ... k-dropper/
and/or along the walls, not too wide strips, so the current and fish could easily access the space between the grass and the wall, but the big fish couldn't hide there.
Couple of constricting issues:
[1] the astroturf in the OP above is $1.68/sq ft, roughly 3x-4x cheaper than the grass squares made specifically for fish tanks, plus
[2] I've had these latter squares and the plastic blades / bunches can be relatively easily pulled out of the holding mesh, they are made with small(er) fish in mind, so the large 3ft-5ft fish may destroy them by accident or by simply swimming and brushing up against them often and when hunting around them. I don't know but I guess that the astroturf is made stronger and handle full human weight, cleats, etc., after all humans have to walk, run, engage in sports on the turf.
My plan is to not have a separate biofilter and, as far as the maintenance, to only wipe the front glass and filter out mechanical waste. But then again, we are back to having to vacuum the mechanical filter mat every so often, so maybe I should simply hook up the 10K to the 15K sump, as hard and as much work as it would be... But then again, I am mulling over making the 10K our first brackish tank (cheap brackish water), so that would exclude using the 15K sump which is being used for 3 f/w tanks.
