Help. Did I hurt my f8 puffer and another question

[Mandalynn87]

Hello. 2 questions pls.
1st
Im a new f8 owner. I absolutly adore him. I went to 3 lfs yesterday and asked for their pest snail hich hickers. Bought a small 1 gallon tank and decided to try to breed them. Gave one to my guy. He really seemed to struggle. Kept spitting it out. He broken it down to about half. Then I took it out because it was slurped up.
I did some research.. looks like i probably gave him a Malaysian trumpet snail. And apparently they are very hard and we aren't suppose to give them to our puffers. It can break their beaks.
Stinks because I was pretty much given all trumpet snails. Petco has more like the bladder type, but I was more comfortable getting things from the lfs like aquarium arts and only fins.
Anyway how would I know if I broke one of his teeth. I gave him a krill after and he ate it.

2nd
I bought him in freshwater.. so his tank is fresh water. I want to switch him to brackish. But im terrified to do it wrong. I was thinking marine salt mixture of 009. And then as I replace tiny water changes. Add that in. But I dont want to shock the guy. He currently in a 10 gallon.. however it is an odd shaped one. It's short and longer and wider then a 15 gallon. I have a tank size restriction via my apartment, however I was told since he was a horizontal swimmer, that the type of tank I got would be acceptable. Hopefully that is true.
Not sure if it matters..but I've kept the parameters at zero for nitrates, nitrites and amnonia. . And I have a ph of between 7.8 to 8 ( hard to tell which color it is on the test) we have pretty hard water where I live but I havnt tested that. I use tap water, a conditioner and add prime brand "stability" into my tank.

Thanks for your help.

[Pufferpunk]

Welcome to the world of pufferkeeping! They sure can worry us, can't they?
Lots of great articles for you to read here:
library/category/feeding/
library/puffers-in-focus/fig8/
viewtopic.php?t=19348