Personally, I'd avoid it, especially if they are mated pairs. Honestly, it sounds like it would just be absolute savagery, as both are territorial and get really aggressive when breeding. Why not try getting a male cockatoo and 2 females?
No. The size disparity between the two species is too great. And kribs can be fairly aggressive when breeding. Either a trio of apistos or a pair of kribs, with suitable dither/target fish, would be a good idea for a 29g, but not both.
well i already have the kribs in my 75 but my neighbor breeds dwarf cockatoos so could i put a pair of dwarf cockatoos in a 20 gallon. Also could dwarf cockatoos be kept with bolivian rams in a 29 gallon.
Yeah, you can keep a pair of cacs in a 20g no problem. Just give em lots of cover. You can keep dithers with them.
and yeah, you can keep rasboras and tetras with them provided you have enough space. Also, as far as killies go, keeping rivulus species with them is a suggested 'biotope' thing.
I have a 29g and tried it myself. The cac took over the tank and the rams were forced to hide. It wasn't the the rams got beat on, they were just forced to keep a really low profile. For some reason the rams were just obviously other cichlids and the apistos seemed to target them above and beyond the tetras and coriies. The rams were only about 1.5 inches. If your try it get big full grown rams and put them in first. If either pair tries to breed you will have problems in a 29g.
I also found the tank kind of busy with both types of fish, and the bolivians got overshadowed by the dynamic behavior of the apistos. I would suggest getting a 2nd or 3rd cac female instead. I ended up putting the rams in a 10g with a low light theme. They look great in there, and their behaviors are much more evident when they don't have to worry about the apistos
Hatchet fish and black tetras make good dithers. As for cory cats my cacs tolerated them even when spawning, but my panduros will not allow them out of the heavily planted portion of the tank.
I was going for the "two dwarf species in a 29g" dream myself. The fact is with a harem of cacs, you don't need, nor would your tank look good with another dwarf cichlid species. If you must try it, have a cycled filter running in a 10g or 5g bucket as an emergency hospital/solitary/recovery/fry raising/quarentine tank. Everyone should have one when keeping Apistos. You never know when "personality conflicts" will arise with these guys.