shark troubles - aquarists please help

[shark66]

Dear list,

I'm a graduate student studying feeding behavior of the chain catshark (or chain dogfish), Scyliorhinus retifer, for my thesis work. I've been having some sudden tank troubles though. These sharks seem to be having difficulty in moving around, almost like their muscles are cramped, and swimming extremely erractically. Additionally, many are dying and coming up with hemorrhaging on their skin. Recently a protein skimmer blew, taking most of the water out of the tank (150-gal), which I quickly restored before these benthic sharks became exposed. I lost one that day, and a few more the next (stress? oxygen levels?). Do you think that the sudden addition of new water (tap + instant ocean w. chlorine chelator) has caused these physiological changes. I'm wondering if any of you out there have professional experience in working with sharks or other elasmobranchs (cartilaginous fishes). If so, please email me ASAP privately, and I can send you pics and more chemical info from there. Thank you for your assistance. -matt

 

[reefrunner69]

What are your water parameters? How many sharks, what size?

 

[shark66]

Thanks for your reply.

Had 10 sharks, now down to 4 (due to death), between 35-40cm in length. Being held in a 150-gal tank with mechanical filter, bioballs, sump system with a newly installed hang-on protein skimmer. Water quality has been poor as of late, but getting better. Nitrites are definitely an issue. Here goes:

Ca: 280 mg/L
pH: 7.8 (low)
phosphates (0)
nitrite: 0.5
Nitrate: 40
salin: 20-25ppt

I should also mention that this main tank (tank #2) is connected a 55-gal tank (tank #3) used for filming experiments, the shark in that tank seems to be doing much better.

 

[reefrunner69]

The hemorraging is indicitive of ammonia and nitrite poisoning, that's not all that causes it, but 10-15 ft of sharks in a 150g tank will get you there quick. I'd look to water quality as the issue and know that that many sharks at 12" + each is gonna require a much larger tank with a much larger surface area even with only 4ft of sharks left.

 

[quarryshark]

It may be a tempory quick fix. But increasing your water volume may help your water quality. It won't be a permanent fix, they need a much larger system. But in may help in the short term as long as you don't add any animals.
Increase the water volume through the use of a large plastic container (s). I would shoot for at least 100 gallon volume to start. The more the better, these fish are not only large, but messy eaters which contributes to poor water quality.
You could use an gravity overflow and a return pump to circulate, basically a large sump. This is a setup I used when I needed to house 9 fish in a 40 gallon tank to treat for a parasite. Is is just a 40 gallon garbage can. For me, it did the trick. For you, something larger would be in order.
Honestly though if you can, a much larger system would be necessary to keep them for very long.
Also, daily partial water changes may help.

 

[shark66]

The weird thing is I've had at least 8 individuals in the tank for almost a year, and haven't really seen any changes unitl the last month. Then again, I've introduced new sharks, here and there. The ammonia and nitrite levels were extremely high, but are much lowered now. The sharks are beginning to swim around better, so I think this was in part due to the stress from the skimmer incident, plus bad WQ. I'm hesitant to add anything else to the tank as so much new water has already been added and I need to let the system settle. I thank you for your help, and will give you an update.

 

[Hara]

I have had experience with ammonia/nitrite poisoning. The bad thing is that even though you fix the water quality issues, it is almost impossible to reverse. At least that was my experience.

 

[shark66]

Thank you all for your assistance, it is greatly appreciated

 

[srgetz]

Do you think that the sudden addition of new water (tap + instant ocean w. chlorine chelator) has caused these physiological changes.

Yes, if you mixed and added to the tank immediately. This large water change with fresh mixed sw probably stressed them a lot. Newly mixed sw is very low in oxygen and the chemical reactions taking place burn the gills / eyes of the fish. And, as I understand it, sharks are even less tolorant than fish to changes in water parameters, so that could explain some of what happened.