Questions on Congo Puffer's appetite

[Puffermania]

Hi, I got my congo puffer about 6 months ago when it was about 3.5in to 4in max. I have been doing regular weekly WC of about 40% and he's quite happy on a 22g tank, albeit it could be slightly bigger. He doesn't swim around much, never explores the cave at the back of the tank and spends time burying itself. My questions are

1) it doesn't eat much, at most a 1.5cm by 1.5cm chunk off the typical market prawns, which is fed every 1-2 days. Is it normal as I don't notice any growth in the last 6 months

2) I've recently try feeding him ghost shrimps 2 weeks ago, which I'm aware of the risks of IP and have my Prazi on standby. I put 2 into the tank, and 1 disappeared which I assume was eaten. The other one seems to take over the tank , displaying audacity such as strolling in front of my puffer, walking on its head when it's half buried. My questions as such are

A) why is this congo puffer so tame?
B) my puffer seems to refused to eat the normal market prawns since, and have rather starve for almost 10 days. I don't understand as it hasn't eaten the surviving ghost shrimp, yet refused to eat its normal diet. I've tried putting garlic flavoured prawns which it chewed and spat out. Only managed a single bite in the last 10 days, and that is after I harassed it by keeping pushing the prawn in front of its mouth for almost 20mins. No IP for sure as I've done my Prazi and water is fine,

Ps: the funny thing is I only suspect the ghost shrimp was eaten as I've found remaining feelers floating around, and my puffer strangely didn't passed out its typical coloured stool for such a big meal.

[Pufferpunk]

Mine gets fed only 2x/week. Slow-grower.

[Pufferpunk]

Mine gets fed only 2x/week. Slow-grower.

[Terrance]

Offer different meaty food beside prawns, such as live worms. I fed red wiggler worms to my former 2.5" congo.

Also you may never see more growth from your congo in captivity.

[Puffermania]

After 3 weeks, he finally ate the ghost shrimp. I had thought he was intimidated due to his lack of aggression. One thing i never understood is why does the congo puffer not show aggressive behaviour towards the ghost shrimp openly? It's always only in the morning that I discovered the ghost shrimps missing.

[Puffermania]

Offer different meaty food beside prawns, such as live worms. I fed red wiggler worms to my former 2.5" congo.

Also you may never see more growth from your congo in captivity.

The lack of growth is just congo puffers? I mean I don't see that with the other freshwater puffers.

[Pufferpunk]

Probably with most sedentary fish.

[Pufferpunk]

Probably with most sedentary fish.

[RTR]

Huge +1 to Pufferpunk's comment on sedentary fish.