groovitudedude;2445046; said:
My fire eel (about 12-13'') seems to have relocated his home into one of my Whisper HOB filters. He only comes out to eat. I know that this has happened to other people, but is it bad? The water in there must be terrible, should I test it? I don't want him getting torn up or severly stunted or anything

If I cover it any more, the water won't be able to flow out of the filter back into the tank. What should I do?
This is a pretty common problem for spiney eel keepers, but you've got to nip it in the butt quick or else it'll spell disaster. Here's some tips for you (if you haven't done so or know already) and for others that are thinking about keeping spiney eels.
What decor do you have for your Fire Eel to use?
- For small/baby eels (≤3" up to about 5+") small ceramic pots (one with about a 3" top diameter and about 5" tall works well in a 10 Gallon tank, though you can always use larger ones too, but they're going to out grow them quickly, but they work wonders in the beginning for your eels) with drilled and/or an enlarged bottom hole work every well, your eels will find comfort and feel protected inside these - without the need to dig around and up-root your plants

.
- For anything bigger than the previous, PVC pipeing is the way to go, IMO; it's cheap (which is good), can be bought in small pre-cut sections (Home Depot sells them about 2'-3' in length and come in 1", 1-1/2", 2", and 3" diameters - which makes it not only easy to bring back home, but also allows you to cut it down to the length you want, while not having A LOT left over), and light weight; because your eels are going to out-grow the diameter fairly quick. I'd suggest you buy a couple different diameters, having your next larger diameter at hand (can't stress this enough, mine out grew it's 2" diameter pipe and ending up getting a "pipesore" [I named the condition after the human equivalent; bedsore] to which was treated and quickly healed, the eel is in good health now and back to it's only self).
As for eel-proofing your filter - window screen works well, but if you have some extra bio-balls sitting around, try interlocking some together to create a "eel dam" near or at the water output area; diameter pending though. Also, securely duct-tape your filter top down (nothing crazy though, as serviceing your filter will be a pain then) so as to prevent your eel from popping the top off and jumping out of your tank (which has happened to me and is scary as #%@$ in the middle of the night, lol - the eel is fine, as I was able to save and treat it in time).
Hope this helps you,
Phleborhagia