I've got a 4foot by 3foot tank with a silver arowana about 10 inch maybe a little more and a black ghost knife fish about 11inch and a common pleco I'd like some fish to stir up my sand substrate alittle more but obviously can't add Corydora as my arowana will eat them any ideas appreciated its a planted tank with rocks but with no additional co2 open to anything as I don't want to stick my hand in and rake it as it will stress my arowana and make him Jump