Blackfin/Columbian Sharks

Question
Currently I have a 55 gal freshwater tank with two 2in black fin sharks. I bought 3 blackfins over a week ago and started them in a 10 gal tank, after some research of their potential size, I bumped up to a 55 gal tank, hopefully I can keep these guys healthy for a bigger tank upgrade, anyhow. I lost one shark 5 days ago while I still had the black fin sharks in the 10 gal, he seemed stressed jerked violently and finally floated to the top of the tank, we did have power outages 3 times that day, ranging anywere from 20 mins to and hour and a half.So the next day I moved the remaining two to the 55 gal, (which I conditioned, let it set and run for over 24 hours before adding the two) and have had them in there for about 4 days. I tested the ph levels yesterday because I notice the black fins had ick (just maybe 3-4 noticeable specs on each shark, and one of the sharks seemed to be stressed and moving awkwardly, kind of how the previous one shark acted before he died. I tested the water, I know stripps are not the best but thats all I have at this time, and the ph level read as high as the stripp would read (8.4), same with the alkalinity(300 ppm). nitrate was about 20, nitrite 0, and hardness was about 75 ppm. Not sure if messing with ph increasers or decreases is considered good practice at the tanks early stage in the cycling process, so I decided to just focus on the ick.  I took out my carbon filters, added quick cure and today noticed there was only one spec of ick on one the sharks, but still I did a 30% water change as well today and treated for ick again. One of the sharks still seems to jerk and spas every now and then, but Im just wondering if there is more I need to focus on as far as the water quality goes. I also purchased some (regular tank salt today) and as well I have sea water salt for converting my tank to brackish water soon. Any suggestions of what I may have done incorrectly? I hope to keep these remaining two healthy and any suggestions on what to look for and/or try would be greatly appreciated!!! Also, was wondering on the average, how fast do blackfins grow?

Thanks,
Paul

Answer
hey.

I have alot of snow here too, and im constantly worried about outages.

The reason for your fishes erratic behavior is the power outages caused a sudden temperature drop from no heaters and they got stressed, thus causing the ich illness.

You want zero ammonia, less than 10ppm nitrate, and 0 nitrite.
These fish do get big fast, so dont add anymore so they have room.
a little info on ich that you may find interesting is it is in the tank ALL THE TIME. Its only when fish are stressed that they get ich.

If the power goes out again, add warm water every thirty minutes so that the fish succumb to less stress.

hope this helps!