Some interesting info i found on this Crabro:
"One thing the aquarist will notice with these fish is that they change color rapidly! Interestingly, males can change color to look almost exactly like the females and, in fact, females can quickly change color to a murky black. Why would did this fish adopt this color changing ability?
I found my answer in Ad Koning's book "Malawian Cichlids in the Natural Environment". Psedotropheus crabro inhabits caves in the lake that are also home to a very large catfish with which it shares a pseduo-symbiotic relationship. While in the gold and black barred configuration, this large catfish tolerates Psedotropheus crabro which picks parasites from the skin of the catfish.
Interestingly, the catfish are also cave spawners, exuding thousands of eggs which make a tasty snack for Psedotropheus crabro. When the catfish spawns, both male and female quickly change to a murky black color to steal the eggs. They then quickly change back to the "safe" barred configuration, somewhat like a cat burgler putting on black before entering a home! "
Malawi are so amazing!