All my fish are dying, please help

Hi everyone,
This is my first time in the forum and i am a week old virgin to marine tanks.
I am having major issues. I bought a tank 7 days ago that had been established for 10 months complete with live rock, original sand/gravel and a humbug damsel, blenny, nemo fish, blue/yellow damsel, pearl green chromis and a rabbitfish. The day later i bought another nemo and a regal tank along with a piece of soft coral, two fire shrimps and 3 hermit crabs.
I climatised them gradually adding water to the bag over 2 hours, the day later the humbug was gasping for breath then disappeared never to be seen again. The day later the rabbitfish was covered in whitespot. My water tests were
PH 8.2
Phosphate 3
Nitrate 100
Nitrite 0.1
I did a 5 gallon water change (i have a 160l reef tank) and put some PH buffer in.
The next day PH 8.2
The day after the regal tang was absolutely covered in whitespot. I added some Myxazin and did another 5 gallon water change.
Two days later Dorie died, another 5 gallon water change. Levels were
PH 8.1
Phosphate 1
Ammonium 0
Nitrate 10
Nitrite 0
Now, the next day all my fish look ill. I have carried on using Myxazin daily as i noticed the whitespot had returned on the rabbitfish. The smallest of the nemo's has nip marks on all her fins, the chromis is flapping her fins veryyy fast, the rabbitfish has lost his colour and looks ill with cloudy eyes.
The inverts and crabs are ok though as is the large Nemo (at the moment anyway, who known what the morning will bring)
By the way i have only been having the lights on 6-8 hours a day for the stress and only fed once a day.

Someone please please help me find out what is going on. I am starting to think of packing it all in after a week when it has always been my dream hobby but it is distressing me so much, i feel the pleasure of such a beautiful thing is being taken away from me due to the 'slaughter' i am inflicting on my poor fish.

When i have looked at my tank this morning the nemo has died and the rabbitfish is currently taking its last breath. I will catch them both and remove them.
My temp is 75' and the skimmer is effectivly removing the Myxazin so i presume that is working. I am going to stop putting that in from today as it obviously isnt working.
The soft coral tree thing is hanging about floppy but it has been like that for a week now and the LFS says its ok just needs shade and feeding, which i have done?
PLEASE someone HELP!

I'll need to do some research on that specific medication, as I'm not familiar with that name. Many medications are toxic to invert life, but if you have run the skimmer during medicating, and/or have carbon in the filter, this will remove the medication, rendering it ineffective.

The more info you can provide about the tank the better we can help. I can see a number of problems going on, and while frustrating, at least you are asking for help, so please don't give up just yet. You may still experience more losses before this tank becomes stable and healthy, and you will have to be prepared to invest some time and money to get it there... but it is still possible to make this work.

Do you have a hospital tank/quarantine tank set up? What kind of filter are you using, and what media is in it? Give me a chance to research a few medications while I await more information from you. Without a hospital tank, I'm afraid there isn't much chance of saving the fish, only inverts. Ick will spread quickly and continue to get worse unless treated, and with inverts in the tank, it's not safe to treat with most medications directly into the tank because the meds are toxic to inverts.
This is touchy, but not impossible to save and/or turn around. Meanwhile, please don't add any other animals, keep up the daily water changes and increase to about 10%, which will only help improve the situation and help keep the fish from stressing further from poor water quality and remove any medication that may remain in the water.
I will post again later tonight with some ideas for medication that is possible in your specific situation. I can suggest a good size for hospital tank if I know how big the fish are, but for future needs, a good size would be at least 75 gallons, based on the species of fish you have. This tank will also need a filter, heater, and some kind of decoration (plastic or silk plants work well). Can you more specifically describe the symptoms of illness? Try not to leave anything out, 1 missed symptom could lead to misdiagnosis of the illness, as some parasites resemble each other in symptoms and have different treatments to be effective.
Saltwater is an investment, and can be expensive to keep stable and healthy. We can help if you wish to continue...

Sorry it took so long to get back, but I did some research and also consulted with my husband before coming back again.
I brought you some options, but they will take time, patience, and some expense.
For starters, I researched that medication you have been using. I found the company website, and it is posted that in saltwater aquaria, it is safe for fish only tanks. If your inverts have survived, I would call this a lucky break. The 2nd thing I discovered is that the medication you need is for parasite treatment of the ick, but this is a bacterial treatment... so not going to help ick at all.
One thing you can do that will help (alongside of the meds I am about to suggest) is a UV sterilizer. That would also help protect you from future outbreaks. Especially in saltwater, it's a good investment, so one you may really want to consider if reef keeping is something you wish to do.
Are the fish still eating? If they are, even while in the main tank, you can offer them pellet food soaked in metronidazole or quinine. (Use one or the other, not both). This will help treat for anything internal that may be causing them issues, it's an antibiotic. In the main tank you can't really medicate for ick because of the inverts, as I mentioned previously... but if you are willing to set up the quarantine tank, copper would be the best thing to treat the fish. The fish would need to remain in the quarantine tank for 4 wks, while the ick dies out in the main tank. If they are returned any sooner, they will be reinfected almost immediately.
I can go into more detail, but at this point, I have not heard back from you so I don't know if you wish to invest what it's going to take to get this tank well?? I will watch this thread, and if you choose to do so, can then help coach you through the steps to get stable and healthy again.
Be forewarned, due to the size of your tank, the tang will need to find a new home. The tank was horribly overloaded with fish before the deaths... with what remains, if the tang is removed, the rest could stay and you would have a full tank. Animals beyond that would be corals, but no more fish due to waste, space, and oxygen levels, among other things. So, what do you say? Shall we try to save what's left?
(Oh, and minus the tang, a quarantine tank could be downsized to about a 40 breeder, which would make things a lot less expensive; and a good filter would be a sponge filter, which also isn't real expensive.
I'm all about saving money wherever I can, so if that helps to sway your decision...

I would also suggest checking your Calcium levels (should be about 400) and specific gravity/salinity (should be 1.023). That also will greatly affect the fish and inverts.
I hope this was of some help...

Patience is what is needed here.

You should not add anything for about 2 months after moving a tank unless very experienced. You've upset the natural balance in the tank when it was moved. Then you added so many life forms all at once. It was a one/two knock out. The added third punch was the territorial dispute and subsequent aggression you've now experienced when adding new fish to established tanks. This needs to be done very slowly. You will need to wait this all out for a few months before proceeding with more fish.

Sorry it has taken so long to update you on the tank situation but all the fish eventually died so we took the chance to have a holiday before starting again!
The Mexazin didn't kill the 2 fire shrimp or hermit crabs, that is all i now have in the tank.
The death of the fish has still never been diagnosed, they all seemed to have different illnesses ranging from white spot to wounds on them. The last 2 seemed to have fin rot and where then eaten alive by the crabs? I was extremely distressed by the whole situation so am now continuing to do water changes every other day and concentrate on building the corals up before adding more fish. My calcium levels were extremely low but i am now putting an additive in every day for a week to raise this.
My LFS has been fantastic, checking my water every day and giving good advice.
I still love the tank and hope to try again in around 6 weeks time but am going to add a green chromis first and see what happens to that before i try adding any other fish.
I feel i have learned a valuable (and expensive) lesson and think the moral of the story to all other fish lovers out there is research very thoroughly before starting this fantastic hobby.
Thank you to the people who replied to my thread, it was greatly appreciated, and what a fab website.

You're very welcome, we are all here to help. If you would like some help in getting started over, just let us know. We'll do what we can to coach you through it safely.

Remember, patience is the #1 ingredient in saltwater success rates.