Best Food for a Dogface Puffer?

[Palster]

I just acquired a Dogface puffer yesterday. To be on the safe side I currently have it in a 20 gallon quarantine tank. When this fish first arrived yesterday it immediately went into hiding and seemed quite stressed which is not really surprising. It did pick a little at some Brine Shrimp today but what I am wondering is what would be the best food to start feeding to really entice this fish to eat? The guy at the fish store said he had been feeding it Krill which it had been accepting. I understand these fish like to eat hard shelled foods such as prawns, crabs or mussels but I do not want to put too much meaty food into the 20 gallon tank for fear of ruining the water quality (I could always do frequent water changes if necessary). This fish will be going into a 135 gallon tank once it has gone through the quarantine period.