Cat shark died, help please

[jacobzking]

He died tonight. A few things I'm thinking it could have been were low oxygen like someone mentioned... I do have a protein skimmer (hang on back reef octopus bh100ss) and an eheim canister filter, neither which put much flow in the water. I do have a power head that was located near the bottom of the tank pointing straight out (so there was very little surface aggravation). I did move it up higher today to increase O2 but it was too late at that point I think. I also dropped the temp from 78 down to 75, but he was dead before it lowered much. lastly, I lowered the salinty from about 1.024 to 1.022-23 but again... too little too late.

Here's the constant water specs (there was never ammonia in the tank like I had thought there was... improper reading from wrong spec card)

125 Gal
Ph 8.2
Ammonia 0
Nitrite 0-minimal trace
Nitrate 0
Salinity 1.025


Is there a way to diagnose what killed him so that it doesnt happen again? The only other fish in the tank are the 9 damsels that are doing fine.

How should I proceed from here?

If you watch my youtube videos, in order of about a 6 day period:

"Banded Cat Shark" looks happy and healthy, 5-6 days ago. eating well.
http://www.youtube.com/user/jacobzking#p/u/3/rImDk-4uEvM

"Sick Cat Shark" about 3 days after the first video... has a big red spot on his left side that continues on to his belly a little, looks bad, and some other small red spots randomly on fins (still active but wont eat)
http://www.youtube.com/user/jacobzking#p/u/1/-tCp2aoxYAw

"Cat shark a little pale" VERY lethargic, rapid breathing, wont eat, feels stiff already but the red spots have mostly gone away
http://www.youtube.com/user/jacobzking#p/u/0/zMiHcWgkpZk

I'm trying to learn from this and I feel terrible about Mr. Shark passing, enough to almost cry. Any help would be appreciated.

 

[luckydog104]

I don't know for sure but looks like an infection to me. How long did you have him ? He could have scraped his side causing that spot ( infection ) . I am no expert on sharks but I do know that infection is a problem with them.

 

[luckydog104]

Something else I just thought of was copper . If any thing in your tank has been exposed to copper sharks are very sensitive to it.

 

[Brickyardgreg]

Maybe it was stressed due to tank size. No shark belongs in a 125

 

[SwampyBill]

If your LFS guy was so reputable, he wouldn't have sold a knowingly diseased shark to a noob with a tank barely cycled (at least he 'fessed up to it...) Best suggestions I can make are find another LFS, get plenty more LR for that 125, & a better skimmer. That R.O. bh100ss is only rated up to 90 gallons.
If you want long-term success in this incredible hobby, I'd also suggest you slow down & read up on your potential purchases BEFORE you buy them. & go with much hardier stock (in an appropriately sized tank). A Cortez ray & a Cat shark don't belong in a 125gal; & anemones won't thrive in a newly cycled tank. Are you acclimating the nems to your new halides? Good luck...

 

[coralfish]

Disease and stress. The tank is way too small for a shark. Also looks like he was sick when you got him.