if your unshure of oragin of the gachua i would play safe and head for lower tropical temps ,around 25deg , then if you must add tankmates personally i would look towards things like either birchirs plecs ect for bottom and something like larger rainbow fish for top , nothing that is going to scare the gachua and nothing the gachua can terrorize . as iam shure you know all snakeheads really belong in a species tank , but if that is simply not an option for you i would suggest the above as about the safest mix , unfortunatly when it comes to snakeheads there are zero shure things
cheers col