I think that would be a bit overstocked for a 40gal Tang tank. They don't usually appreciate being overstocked like Malawi cichlids do. They are also more sensitive to water quality so you would need to have excellent filtration & excellent water change habits. I would take out 2 of the Leleupi & probably one of the Brichardi if it were me putting those fish in a 40gal. I think you would really need 55gal to have your full stocking list together.
The Calvus could get rather aggressive if the pair decide to breed at some stage to so you may need to have a second tank to remove a few of the other fish to during breeding times.
K. How would this be;
And then 2 or 3 pairs of a tougher sand shifter or shell dweller.
As for the filter, I'm building one so I can make it as powerful as needed. I do a water change every week so I'm fine in that aspect.
You might be able to get away with that list IF your very clever about the decor layout. The Leleupi can be very aggressive towards each other if they don't have a clearly define territory each, as can the Marlieri.
So long as you design the decor to suit those territorial needs, it might be ok.
Personally I think a better list would be:
1 x Calvus,
2 x Leleupi,
3 x Marlieri (1M & 2F)
1 x Neolamprologus Brichardi OR Pulcher
1 x Tanganyika Clown Goby (Eretmodus Cyanostictus)
Given that the Calvus is a predator with small fish making up a good part of it's diet, I don't think it would be wise to keep the smaller Shell Dwellers. Maybe 2 pairs of Ocellated Shell Dwellers (Lamprologus Ocellatus) would do ok.
Ocellatus were one of the few shell-dwellers I was thinking about, as they are more agressive than others. I like the list, just wondering what the behavoiral differences's between Calvus and Compressiceps are? The only reason I'm leaning to the calvus is because they stay smaller, but I was just wondering if there are any other difference's.
Calvus & Compressiceps are very similar in size (6" for both) & appearance. There are a few subtle physical differences. I believe counting the rows of scales on the head is one way to tell. The Compressiceps usually have bolder vertical stripes but not always. Behaviour wise they are also very similar. Both are predators but the Calvus is more likely to go after eggs & fry where the Compressiceps seems to prefer slightly larger juvenile fish. The Compressiceps tends to be the more active hunter but both don't generally move around a whole lot unless there is food on offer or they see the opportunity for an easy feed. Shell Dweller species make up a good part of both fishes diets (more so the Compressiceps) & they have developed the laterally compressed body so they can get further into cracks & crevices to suck thier prey out of thier hiding places. Neither are particularly good tank mates for sall Shell Dwellesrs IMO. Calvus & Compressiceps are in fact shell dwellers themselves but often it is easier in the aquarium to provide caves made of rocks rather than try to find shells that can accomodate a 6" fish.