Hi I’ve had tropical fish before but when I was younger. I’ve now got my own place and got a 30 gallon corner tank set up and cycled for about 6 months with 7 guppies and 6 corys all going great. So with the corys staying at the bottom and the guppies at the top I was thinking of getting a shoal of 12 cardinal tetras for the middle. Would this be ok or is that too heavily stocked. Also the tank has a few rocks and drift wood with a reasonably heavy planed back area. Thanks