I had a tank a few years ago, till my dog started gnawing on the tank stand causing a disaster.
It was a 110 gallon long tank.
I started out with the typical angel fish, some neons, and gold fish and so on.
I soon grew bored, and bought a Jack Dempsey, and a green terra.
Bad move.
They quickly began destroying the other fish.
So I figured that since I was going in that direction, I would buy a few Oscars.
They were tiny. About the size of my thumb nail, or a quarter.
Some were albino, most were black.
I started feeding them ciklid tablets....no good.
Then small amounts of baby gold fish....WOW! they wiped them out fast.
Some of the Oscars were getting bigger than the others and started eating them.
I moved onto Pacu's (a form of pirrana). They took care of the rest of the Oscars except for the two big ones.
2 big Oscars, 2 big Pacu's. I needed more fish.
I bought 2 snake heads. Nasty mothers. The fish would fight from time to time, but nothing serious.
But after a while,
Little by little, the fish were being killed by the snake heads.
But the sole survivor was one of the Pacu's.
He killed everything in the tank.
And yes, I fed them A LOT!
Hundreds of gold fish a week.
Now I had this giant tank, with one big fish that killed everything. I was affraid to put my hand in the tank.
What to do???
I bought a wolf fish. Holy poop! killed the Pacu in one day.
He was the sole survivor.
After that, much later, the tank fell over, and that was that.
Thats was a long post. sorry.