Ammonia spike in Pacu quarantine

[FinsandFeathers]

My wife acquired 2 Red-bellied Pacu juveniles, that will eventually go into our 400g "monster" tank. However, as they were only 3 and 4 inches when we got them, we thought putting them in a tank with a Silver Arrowana, Clown Knife, and 14 inch Oscar may have been tempting fate, so we put the in a 29g grow-out tank temporarily.
In just a couple weeks, they've each grown by at least a quarter of their original size.
My wife clips kiwi and zucchini in the tank daily, as well as feeding them slivers of brazil nuts, other veggies, and occasional brine shrimp. They don't seem to like the skin of the kiwi and zucchini, and every water change (about every 4th day), I find pieces of the skin in the substrate.
Today, they were acting strange; no appetite, rapid breathing, lethargy, etc, so we tested the water. High ammonia, as expected, after only three days.
So, we were hoping the people in the forums can settle an argument.
I think the ammonia spike is due to rotting kiwi and zucchini skins. My wife thinks it's because of the increased bio-load of the fish due to growth.
Could someone please tell me, and her, that I'm correct?

 

[V227]

It's likely both factors are contributing to the ammonia problems. I've read some of your posts and know you guys got skills and will easily solve the problem. I like Pacus and kept them several times when I was a kid. When they "quickly"outgrew the tank, back to the fish store they went. It sounds like you are providing the baby Pacus a top notch diet. Be sure to post pics as they grow, I'd like to see that huge tank.

 

[coralbandit]

I had red and black pacus back in the 80's in my 135
They were with a 16" knife ,14" arrowanna, stingray and 16" SNAKEHEAD..
The red bellies used to irritate the snake head to no end nipping at him..
I am not sure where your ammonia comes from ,they are large waste producers...
The story is to say the red bellies were only 4-6 inches when I had them..
I think you can get yours in your big tank safely whenever you want..
They were the pesty trouble makers of the whole tank !

 

[FinsandFeathers]

Thanks, guys.
It figures that on the rare occasion I'm right, I'm only half right.
The ammonia problem is easily resolved: more frequent water changes, and activated carbon added to the filter.
I'm surprised to hear that your pacus picked on your snakehead, Coralbandit. I had always thought snakeheads were the meanest of the mean.
Once they reach 8 inches or so, we plan to rehome one of them, if possible. From what we've read, they don't get along with each other as adults. My wife is trying to train them to take food directly from a pair of feeding tongs before we put them in the large tank. She's worried that the arrowana and oscar will gobble up all their food before they get a chance at it. Watching them eat in the 29g, I don't think it's a worry. Proper diet is a worry, however, since they're going in a tank with carnivores, so the tongs are probably a good idea.
Thanks for your input.