Although this species is not as fanatic in earth eating as true Geophagus, I would certainly make it possible for them to sift sand.
I once had a Geophagus from a store tank (bare bottemed) which spend the first 12 hours I had it digging trough the whole tank - over 4 square feet. Later it hardly sifted any sand. To me this was evidence fishes can be frustrated, just as human beings. I think Acarichthys can get just as frustrated as Geophagus if not able to sift substrate. They will not mind sifting clay, you will. Thus sand is one of the few compromises
I had this species twice, the first time they were very agressive, but I might heve koept them in too small tankds (`130 * 60 cm, or 130 * 50 cm) with too few (3)
The second time they inhabited a 4 meter tank. They were very peacefull indeed, amongst each other (6) or towards other fishes. However, they died form a very agressive desease, killing all cichlids, exept Heros and Medonauta. Thus I keep only cichlids from this group (Heroini) in this tank.
The second time they did not eat the tiny tetras I had put in the tank previously, the first time I added 4 small fishes, which were (naturally) not directly happy in the tank. Thus the Acarichthys assumed they said 'eat me' and did
I almost lost both one of the tiny fiash and an acarichthys, but after 1 day I could get the corpse out of the Acarichthys mouth
So do be carefull with adding new, small, fishes