advice appreciated

[Pryncezz]

I know, I know, so typical. My first post ends being a DD+T....
Here is the deal: (I'm gonna sounds like a pathetic loser, but seriously, it's NOT MY TANK!)

So, "my friend" has a fish only agressive tank. It's approximately 120 gallons with a 30 gallon sump. Big venturi protein skimmer, 200 or so pounds of rock, shallow sand bottom. UV sterilizer, and a chiller. Two returns. at least a 1200 Mag drive sump pump.

Bare with me... long history here.

He set the tank up thru a local fish store that also offered maintenance. He started with a 55, but quickly upgraded. He had his wood floors refinnished, so dismantled the tank before doing so. Since restarting, this tank has only been misery! The store only showed up once a month at most to change water, never cycled it properly, don't QT their livestock. One dead right after another! EXPENSIVE angels and wrasses, groupers and puffers and triggers, one after the next; gone. The store would come, change a touch of water add 3 fish, they would die and take 2 more with them. BAD SCENE!!!!
I knew about this tank about 6 months ago. I recently moved from Canada to NY and I used to work in an aquarium and pond maintenance company- heading the aquariums. I've worked on 800 Gallon systems down to 10 gallon tanks. Both salt and fresh. before that I ran the tank room of a large store for 3 years. Though I still feel that my salt knowledge is so little.

There were 5 fish. a regal tang-6 inches, jewel grouper-8 inches, picasso trigger- 6 inches, NEW Naso tang-8", NEW black Puffer. (my friend really loves his puffers!, but none have survived...)

Naso Tang after three days not doing well. Puffer covered in ich. Naso dead- panic call from friend. Giving up the store- the tank is mine now! I go there and find 3 fish dead. sigh, so sad.

SO- I tested the water and of course the nitrAtes were thru the roof! ammonia was .025 and nitrItes were 0. I removed the dead, fanned the rock and did a massive water change. Rinsed a bit of the filter media. The puffer was covered in Ich. researched a bit and decided only and best course of action would be hyposalinity. Started dropping the salt that day. left at 1.012 from 1.016.
Next day- puffer looking better, healthy, active. our hopes were up.
by day two he was botom siting with spines protuding from body. I changed more water and dropped the salt. by day's end, the puffer was dead. (really tragic)
I continued over the course of the next few days to lower the salt to 1.009, and kept trying to reduce the nitrAtes.

The remaining fish have been doing well, There was a green algae spike, changed water and scraped the walls- though I liked it and thought it beneficial, though ugly. (I have bought an insump refugium and when I raise the salinty hope to get that up and running with cheato) I have been changing water and rinsing different parts fo the filter to keep nitrates down. BUT, the nitrAtes skyrocketted after my last water change- between 60-80 ppm. ( I did have them in check around 20-40PPM just a week ago)
and the jewel grouper has a white pimple like dot on his chin. It looks like a fresh water anchor worm. It wobbles. This fish is now pretty inactive, prefering to hide out. He used to love coming out to play.
Is this cotton mouth?
I thought that 6 weeks as of today in hyposalinity would have erradicated such parasites and such sickness from the tank?
Is this "just" a water quality issue? (like that's not EVERYTHING?!)
What do I do now?!
Thank you for reading and all your helpfull advice.
I try to keep the PH around 8.0-8.3

[plateboy3293]

First off
To Reef Central
The dt tank has icn and cotton mouth you must remove all the fish and put them in a seperate qt for hypo only kills ich in certain stages so you must remove all fish so thheir is no host. Leave dt without fish for 8 weeks or so. To allow all ich to die treat fish with hypo in qt seperatly when one fish looks good and the 8 weeks are up wait one more week and make sure the fish does not contract ich again. Pm me if you need any more help

[ricks]

I would assume RO/DI for all water changes????