F8 puffer fish's future tank

[Treekami]

Hello everyone! I am new to this forum. I have many fish but my favorite fish I have to say are puffers and bettas. I have one Pea puffer named Bien (my avatar) in her own 5 gallon tank, chili rasporas and Galaxy rasporas in their 10 gallon tank, a betta in his own 5 gallon and soon to have a new friend, a figure 8 Puffer fish! I have his/her own 20 gallon long tank started and almost cycled and ready.

I read up many things about the fry, like how they can be in fresh water for a little while and slowly change into brackish waters. I want to get a fry or a younger one but not sure how to go about this. My question is, After the tank is cycled, should I start slowly adding salt to the tank before adding the puffer in? Or should I place a puffer in the tank after it's fully cycled and then slowly add in the marine salt? Or does it depend on where I get them from and if they are in brackish water or fresh at the store?

thanks for the help and I am glad I found this site!

my puffers future tank: (ps: the rocks on the wood are only there temp. keeping them down until they sink)

[Pufferpunk]

That is a lovely tank but would be better suited for a FW fish. I'm afraid the substrate is all wrong & none of those lovely plants will survive brackish water.
library/puffers-in-focus/fig8/

[Treekami]

The plants are soft and fake, not real. And I read that the F8s do better in sand but also read that sand makes the PH high and mine is over 8.0 already. I also have really hard water to boot. Would gravel be a danger to the F8 puffer?

[Pufferpunk]

The pH of your tap water is >8?

[Treekami]

Yes my tap is 8.0 already like I stated above... but will gravel hurt the puffer is what I am asking.
I will also be getting crushed coral once I turn this tank into brackish tank, but for right now I'm letting it finish it's cycle until I get the F8.

[Pufferpunk]

It is actually the hardness that is more important than the pH. I still suggest using aragonite sand. It will keep the hardness up & will not raise your pH.

[Treekami]

My Gh and KH is high. I don't want to make my water harder than it already is.

[Pufferpunk]

OK then gravel or regular sand is fine.