The rainbows are already in a 40g long. This would just be an option tank for cichlids that are getting beat on by larger tank mates, like jags, GT, or Oscars. I keep the water temp at 78 degrees for the rainbows and they do fine. This temp should be fine for the cichlids also. I think the rainbows are too fast for any cichlids I would put in with them, I just wonder how the bows would do with the stress.