IMO controlling your parents can be difficult if even possible??
I would guess you are doing well under the circumstances ,
but your tanks ....not so well...
Maybe you could ask your Dad if just one tank could be only yours and he would not add to if possible??
Either way tread on doing the best you can no matter what he brings home.
Have you told him of the remarks that fish people are making??
Maybe just maybe you could ask him to read this thread if it would not get you in trouble???
Stunt is slow /less then normal growth.
The product in link has many names but is basically ceramic noodles that have a very large surface area for bacteria to live.Like the Bio balls but ceramic not plastic..
Sponge first to filter out large stuff,then chemicals(zeo) then bio media.