Hi im new to keeping fish only started in january this year and iv jumped in at the deep end went all out and bought a 8.5 x 2 x 2 foot tank . Im keeping african cichlids/ cuckoo catfish / senegal birchir / cray fish / redtail shark.. there all geting on fine but cant seem to stop the africans from flicking on the rocks and sand any ideas please because its driving me mad. thanks