Green spotted puffer

Question
.We have mostly corals in our tank so I am very careful of what kinda fish we put in.. Our fish guy knows what fish we have and he said a Green Spotted Puffer would be good with our corals and the fish we already have..Since we put him in he's doing very well but everyday I get up I have another fish dead or dying.. There are no fin nipping going on becouse I check them. And I have had my water tested every other day and thats perfect.. Could it be the puffer thats hurting them some how and it not showing ?? Or is it something I am not thinking of.. Is there something else that I could check to figure out why my fish are dying . Or is it my puffer?  Thank Valerie

Answer
Good morning Valerie:

This would be extremely hard to determine without me being able to monitor the aquarium. Often times there is an invertebrate (for example a crab) that will be nipping fish during the night.

You could set up a time lapse camera overnight, than review over the footage to help figure out who the culprit is.

Regards,
Dave