Guppy got caught in filter some how still alive? (is it best to euthenise)

I would use clove oil if planning to euthanize. There is an article on it here

Hi, I've had to do this before, and it's a good humane way to do this. Be sure to follow the instructions carefully, so it's a gradual gentile way to die. Sorry for your loss.

If he was stuck to the intake, he's probably pretty far gone, since that doesn't happen unless they are weakend for whatever reason. I'm very sorry. It hurts to lose one of our sweet little creatures, but it is very kind of you to do this in a humane manner.

Here's the article on euthanasia:

http://www.aquariacentral.com/forums/showthread.php?t=148361

If a full size guppy was stuck to the intake, something else is wrong. The guppy was sick before he got stuck. Simply being stuck there would not have seriously injured him, there's not that much pressure. The only exception would be if you had let many of the slots become plugged and the filter is just intaking through a couple.

It would be good to isolate the affected fish and see if you can't diagnose and cure him. While not assured, there is a possibility that he is the first of a disease outbreak. He also may be old or infirm in some way so it' not an automatic epidemic, but take a really good look at him.

Marv

healthy adult fish should have no problem resisting the flow of the intake, even if it is narrow and strong. fry often have trouble because they are small and weak, which is why intakes should be covered.

even sick fish will be able to resist the flow of the intake, but a fish would have to be very ill to give up.