2 4" tiger oscars, tricker has been in 38g at least 6 months, trying to put another 4" in with him (walmart), ive tried walmart in, they fought so i took him out, then took them both out, rearranged the tank, older one was out for a total of about 20 min then put them both back in at the same time, it was ok for a while then tricker started going after him again, seperated them again, next idea is take tricker out, put the walmart in for a day or so, then put the older one back in? not sure though need advice.