Figure 8 Puffers

Question
Hi, I am on my 4th puffer.  Had 2 gsp's for almost a month, before the one stopped eating and died about 2 days later, and the other one died a day later. I purchased another gsp. He lasted a week. I do water changes weekly. I think I feed them properly. Not sure what's wrong. There diet consists of blood worms, brine shrimp, snails, muscles. Oh and cocktail shrimp, which I wasn't sure of at first if I should be giving them cooked or uncooked shrimp, doesn't it matter? Today a brought home a baby figure 8. If there's anything you can think I'm doing wrong, please help so he stays alive. Oh and he's in with a baby fire eel, which eats great and swims fine together, no fights what so ever, and a few live plants.  Thank you so much for any help.

Answer
First off, check with where you buy your puffers as to what they keep their water parameters at and try to keep them as close as possible. Fish can not withstand a rapid major PH change. This would need to be done ever so gradual, a drip system and over the coarse of a few days. Water hardness could also be an issue here as well.
I would skip the cocktail shrimp, you eat the yummy meat, but give the legs and tail-fins to the puffers and give them some Blackworms, Krill and live adult brine shrimp instead, along with the snails, muscles and bloodworms. They must have food with shells, the crunchier the better to keep their teeth from overgrowing.
The addition of live foods puts a load on the filter as well, and in the case of Pufferfish, as you see, there are clear advantages to keeping water quality as a good as possible. Try to change 25 percent of the water at least two times a week rather than weekly when feeding live foods. I would add "lots" of plants too. There are many plants that will help you with your water parameters, they will absorb the nitrates, nitrites, ammonia, etc.
Hope this helps. Send a follow up if you have any more questions.
Good Luck.