Yes....those little orange, cheesy, crackers. Goldfish crackers. Our almost 3.5 year old thought his fish needed to eat goldfish crackers. I am sure the fish LOVED eating them, but the tank didn't like the PH balance shift and it killed almost all the fish! We tried to remember the last time we gave our kids goldfish crackers and it was been 2-3 days. So our 10 gallon tank of 40 fish had been polluted for a while. The end result? 35 dead fish.
Only five of the fish survived. Of course they 35 dead ones received a proper burial....
No worries - this fish tank started with five fish just two years ago...and they kept breeding and breeding...so I am sure they will multiply yet again and our missing 35 will return.