Really need advice.

Sorry to hear you are having so much trouble with your fish :(. The only thing I could possibly recommend is to get a cheap rubbermaid tub and put the fish in that while you try to disinfect the main tank, since you're right, you can't put them in the QT with your shark.

Assuming it is/was ich, in the future I'd definitely recommend the salt/temp. treatment. Some of the medicines they sell can be way too harsh for many fish and, IMO, cause more issues than they are worth except in extreme situations.
 
what are the water parameters?

how well cycled was this tank? was it cycled? it is quite possible that ich may be only one Sx of what is going on. it is possible the tank is suffering from water quality issues affected by the biological cycle.
 
I would suggest finding some way of increasing surface agitation and maybe creating a stronger current through the tank if it is oxygenation problems. What are the disclaimers on the medication?
 
I think star rider might be right. The tank was semi-cycled when I started adding fish but I used liquid cycle and it had been a few weeks so I thought Id be o.k. Then I added fish with ich so I'm sure there are a bunch of problems with the tank including spikes and such but If I do too many water changes its hard for the medication to cure the ich so I'm still open for suggestions.
 
as long as you treat the amount of water you're adding to the tank(ie, if you pull out 10g of water then you should add 10g of treatment) the medication should still be effective, formalin and malachite green are potent combo that should be used a lowered dose(50~75%) for sensitive fish like cats and tetras. my suggestion would be to discontinue the meds for 3 days, do a 20% wc each day and put some carbon into your filter, then when the fish look a little less stressed add in the meds at half dose and give it a while to work(3~4 days) with no water changes and after that if there is still ich then do a repeat of 3 days w/ no meds and lots of water changes and dose again at 75%
 
O.k so I got tired of the water getting cloudy no matter how many water changes I did and the fish looking like the ich was getting worst so I did a 80% water change/gravel vac and took everything out of the tank except for the bubble stick/heater/thermometer/filter. I put a bit of liquid cycle in, some stress coat+ and the recommended dosage of salt. The heater is as high as it goes so if this doesn't do the trick, I don't think anything will.

I noticed My drift wood had plant life (maybe fungus?) growing on it and I remembered that I didn't boil it since I got it at petco and It sunk automatically. Maybe this played a part in messing my water quality up? Either way this is my last hope, and if it doesn't work I'm going to try and see if the lfs will take my fish as I clean the tank out completely/re-start the entire cycle.
 
That's what I would do! My LFS has held fish for me I just put down a deposit of 1/2 the cost and they held a Picasso Trigger fish for me until I had things settled with my salt water system.
 
treat your cat as a scaleless fish --- remove any activated carbon and use half dosage or even less and treat the whole tank with that half dosage. and spring for a new heater.
 
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