This is getting a bit ridiculous.
At least once a week there is a new thread about a new fish you've purchased. They're all going into that same tank with the blue gravel. You say you've only got one Geo now; what happened to the one you purchased within the last month? Are all these fish dying? If so, that should be a wake-up call that something isn't right.
How old are you? Why is your dad always against what's in a fish's best interest?
I've been keeping fish since I was five and breeding angelfish since I was twelve. I don't think that age is any excuse for a lack of care or responsibility, especially when it comes to that of a living thing that is dependent on you for survival. I researched and planned every fish that I brought home. If it didn't work out, I either made changes or I did the responsible thing and took it back to the store. My parents never cared what substrate or decorations I used, so long as I was being responsible and caring for the fish properly.
These weekly new purchase threads are frustrating, especially when the past newly purchased fish seem to disappear from the tank. It's worrying.