I wouldn't split that group; large Paretroplus can and do get very agressive in small groups.
1 pair in a breeding tank, yes. 4 adults in 1 tank; no. recipe for disaster.
also; breeding season of many African fish starts in march, pril.
so you can expect the fish to be uninterested in breeding at the moment
fiddle around with temperature! keep them a few weeks or months at 25' C, change a lot of water and then ramp up the heater to 28-29'C.
you'll see a change right away
certain food helps to get the fishes in breeding condition
for large Damba's mollusk feeding is the key. Paretroplus menarambo is like p maculatus a specialized snailfeeder. the protruding teeth in the upper jaw are for winckling snails out of their shell.
feeding with live Ramshorns (Planorbis) or Pondsnails (Physa) is a good trick, although in my experience the Damba species of Paretroplus also feed on Trumpetsnails (Melanoides), Applesnails and their eggs (Ampullaria, Pomacea) and they also relish mussels, cockles and squid.
other good food to get all kinds of fish in spawning mode: mysis, krill, black mosquito larvae, California Blackworms, gammarus and Ad Konings' famous Shrimpmix, the stuff Tropheus breeders use.
i have a large group of P maculatus and often spawns, but as mentioned; they're notoriously sloppy with fertilisation and breeding care. so no larvae here either.
at the moment they stopped spawning and my experiences with many other African cichlids (both Rift and riverine) point at low season for them. it's not yet breeding season for many African cichlids
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