Green spotted puffer URGENT HELP?

i'm at college but my boyfriend is watching my fish back home for me. i've had my fish for roughly 6-7 months in full marine and he's always be fine. but this morning my boyfriend found him stuck against the air filter tube that sucks up waste and so he pulled him off but have to go to class. when he got backbone, the puffer was resting on the rock, still breathing, but there's a red string coming out of his gill.
he checked the parameters and everything is fine. could it be parasites? or could the suction enjoy damaged him internally? what would that be hanging out? he's trying to swim around now but he's not doing to well brought-up and it's breaking my heart.
any suggestions or is it all bad news? =[
gratefulness
Changing a betta's cistern?
Answers:    The red string coming out of the gill is likely a gill fluke, which is a type of parasitic worm.
If that's what it is, the fish should be put in an isolation tank and treated next to a parasite cure, and any other fish in the tank should be watched closely for signs of one affected.
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That's a gill flute. They burrow into the fishes body and suck the blood from it. Sometimes they can be removed with tweezers but be careful he does not start out the head inside of the fish. Treat tank for parasites.
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