Puffers in smaller tank

Hi everyone new to the forum!
My hubby and I have been running a tank of tetra and danios for a few months now. We recently got a 90l tank and decorated and planted today. While cycling that for a few weeks before moving the clan, we have some time to choose what we put in the other tank. I absolutely love the green spotted puffer but I am struggling to find info - all of it seems to conflict. Can i put 2 to 4 GSP's in a 29l tank? Some say no, others say yes. I do have 2 nice, small hides and some plants where they can hide but I don't want to disadvantage the fish so I want to get some info from experienced aquarists before I get any new fish.

 

Gsp do not do well in community tanks, they will eat other smaller fish and that is not healthy for them, also they are prefer brackish ( semi to full salt water ), while they are young they can survive in normal water but once they grow bigger they will need brackish to full salt water, without it, they will not do well and will die eventually, they need snails as part of their diet, they have (rabbit like teeth) that will overgrow if not feeded enough snail or hard shelled foods, i have a snail breeding tank only for mine, its no joke keeping these fish, pls do propper homework before buying them.
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Green Spotted Puffer Fish Care, Feeding and Tank Setup | PetHelpful

 

Maybe I didn't express myself correctly, I don't want to add them with any other fish, the ones we currently have are moving to the big tank as soon as it is ready and the tank is open for only puffers. I would like to know however if I can put 2 to 4 puffers into a 29l litre tank - with no other fish.
Thank you for the other pointers, it is very helpful.

 

No you cant. They grow to large and as Hein said, require a full brackish setup in order to thrive and survive. You could always try pygmy puffers

 

Recommended minimum tank size for 1 - 2 gsp is 100L, i have 2 in a 150L and they do well for a few years now, but they are not schooling fish, they are loners, each one have its own hiding place and i seperate them when feeding as they tend to get aggressive, so 4 in one tank will cause major fighting among them

 

There are also dwarf puffers you can keep 3 to 4 in a 30L. If you can find them the amazon puffer is the most "community" suitable puffer. There are also the mekong and humpback puffers which can live in a 100L but are highly aggressive and need their own tank. All these puffers are completely fresh water.