For about a few months I've been the owner of a Fang's puffer (Tetraodon cochinchinensis).
I have the feeling he isn't eating very well. At the moment I feeding him cockels, mussels, and parts of seafruits.
I've tried bloodlarves but he is just spitting them out.
I'm trying to breed snails but at the moment there is just nothing happing, the same with my breeding guppies, not a singel baby in 2 months
If he's eating a cockel he just takes one nip, and then leaves it.
You should check your water parameters - ammonia, nitrite, nitrate, temperature - and report them here, just to be safe.
Possibilities which need ruling out are: tooth overgrowth, constipation, and internal parasites. By the look of your puffer, parasites are not the issue.
You might try some other foods - live blackworms, live ghost shrimp, frozen uncooked shrimp (thaw first), or live crayfish.
To breed snails you need to feed them pretty heavily. What kind of snails do you have?
My Puffers: Puffers I have kept: T lineatus T miurus A modestus T biocellatus C valentini C coranata C papuan C lorteti DPs suvattii burrfish T niphobles
My T turgidus seems to be very picky. Many foods other puffs love, he turns up his nose at. He does love earthworms, shrimp, crayfish, or anything on a shell.
You are getting sleepy... you only hear the sound of my voice... you must do water changes... water changes... water changes... water changes...
My waterparameters are:
Temperature is 28 degrees
Nitrite is not measurable
PH= 7.75
Unfortenately I do not have test for amonia and nitrate.
The snails i'm trying to breed are the apple snail and the pond snail, they are located in a big aquarium with other smal fishes.
Since the moment I've got my puffer, he is happily living together with a japonica shrink. So I rather don't feed him shrinks because the japonica keeps the algue away, and probably when I feed him shrinks the japonica won't live very long .
How can you see your puffer is having tooth overgrow or constipation.
Mine is only 1.5" Out of all my puffers he is the pickiest feeder. At this size he gets fed every third day and even then he doesn't always take the food. I wouldn't worry too much! Try to cut back to every other day then every two days.
Some call it a product of a mis-spent youth, I call it Rock n Roll !
ok I will start feeding him every other day or every two days.
He doesn't seem ill or something and has periods he rushes through the whole aquarium.
But I always thought that puffers were big eters.
Many puffers are pigs and will not stop eating (well seem like they wont.) And then you get some who eat just on occasions. Puffers are like people, they are different. But because they are all different in ways does that make them the same?
My Puffers: Puffers I have kept: T lineatus T miurus A modestus T biocellatus C valentini C coranata C papuan C lorteti DPs suvattii burrfish T niphobles
The active hunter-predators are the hungriest, The higher the activity level, the larger the appetite. The semi-lurkers such as yours do not need daily feeding once ~2/3 to 3/4 of adult size. None of my adult fish are fed every day.
I''ve tried your tips and it's working. I didn't feed him for two days, and after the two days he accepted the food. I've tried those (un)frozen shrimps and he just loves them. He eats two or three every two days, and he goes wild for them he don't wasted a thing.
And luckely he still hasn't try the live jarponica shrimp, that one is still walking around.
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Some call it a product of a mis-spent youth, I call it Rock n Roll ! 
