Fin rot - ich?? What is it? Lymphocytis?

I am currectly running around 300 gallons in my basement, and when a fish comes unders stress, a breakout of ich lasts short term - and likely goes away in all my experience. I started a tank for my girlfriends 10 year old daughter, I drilled a 20G L tank and designed an overflow. A ten gallon sump with UV Sterilizer - protien skimmer, bioball drip area, and heater are in the sump. Basically a mini tank of my 120. Lighting is a 10K and Actinic. The system started fine and was up and running - cycled with live rock. The heater broke and killed 2 clowns that were in the tank, The tank was then left alone for a while and I decided to get the magnesium based material out of the sump, give it a good vaccume and clean it up. A baby sailfin was introduced and bam, it got hit with the fin rot. Ich looking, but then the cottonmouth. It ate the lips right off the fish. I tried to treat with API natural product - no luck. Then tried to mov to hospital to treat more aggressive. It died fast. Now it has been 3 weeks - no life in the tank, packed with liverock and some frags that ended up drifting around in my tank. I figures if the tank was empty the host would be absent and the virus or bacteria/fungus should die. The anemone was doing well and is the only thing that hasn't been effected. I fund another pair of perculas. they looked harty and I introduced them. They were fine for 3 days, now ich, and looks like a little rot on the fins. I picked up some erythromyacin by API and started to do a 1 hour drip a day in the I.V. bag that I have. ( No matter what chemical introduction , I always drip solutions). This is the 2nd day and I have seen no improvement. Does anyone have any suggestions on how to get these clowns through the stage of adapting to their new environment? I have never really dealt with this and I guess on the level of one fish after another it concerns me. the waters Ph, alk or dkh is good, 8 ph, dkh 10, and calcium at 420. No ammonia, and no nitrites. Heres a few pictures

Some picts

I thought I read on the site that it is an 8 week time span with no fish for the ich to die off with no host fish if the daughter wants to see some life a couple of shrimp maybe?

yes, for ich (and probably everything else) the tank needs to sit fallow for 8 weeks. You can inverts to your hearts content, but not ich.

https://www.livingreefs.com/oh-no-have-ich-do-do-t30950.html

But it doesnt really sound like they are getting ich. Ill think about it and see what i can come up with.

Thanks. I think we should have left the tank longer. Hopefully the erythro knocks it out. They just started to eat a little. Should have hatched some brine shrimp. Now that I look close I can see that there are small white dots, and the dots are raised underneath. I would take a closeup but the camera I have is made by mickey mouse. I do notice it looks like it cleared, then looks like its back. API said it was safe to dose in the aquarium with anemone and reef. We do have a hospital here but it isn't completely cycled. Was thinking perhaps I should get some small live rock in there to speed it up. I don't want to hit them with ammonia and just make them worse. Any ideas are helpful. Atleast this doesn't look as bad as before. I'll try a pict.....

Any that says reef safe wont actually cure the ich, it will only deal with the visible life stage of the parasite. And from your most current description i would say that is ich.

Also a QT tank doesnt need to be cycled, any real meds will kill the bacteria anyways. Just check the water daily and do a water change if you see any of the levels start to creep up.

Read that link i gave you, it has lots of good information on there about to deal with ich.

well. with the heater breaking months ago, and the debris that was on the bottom all vaccumed out , all I could do is strip the water for metals. Nothing showed up. Tetra stated it was magnesium, do a small water change. Nothing survives in this tank. Thank God it isn't the large reef I have. With the loss of 10 fish now, I am beginning to think the waters poisoned. Fish that enter have a life span of 2 to 4 hours. Ammonia 0 , nitrite 0, small minute nitrates. phosphates very low, I cannot find anything wrong with this water. Started a bag again of carbon in the sump, added a better skimmer - a seaclone and a uv stilizer. Still no doubt. So do I leave this system for the 8 weeks with the anemone the shrimp and the corals? No fish and just constantly vaccume and carbon the water? Because I am ready to give all an RO-DI bath, fill the tank with RO-DI while I house all the corals in my sump of big tank, then refill the tank with new water. Returning the inverts corals to the tank after the new water settles, then wait anyway for fish. I am growing impatient with the tank only because I seriously think it's poisoned. But . . . wouldn't the anamone been hit long ago? It is fine?

Ya, that is really baffling to me too. And i am so sorry i didnt look up those symptoms to see what i can find.

But it sounds like it might be marine oodinium, which is bad news. It almost always fatal and its a fast, nasty killer.

Marine Oodinium; Information about Brooklynella & Amyloodinium Ocellatum

And i have no idea what the next step is if that is what it is. Maybe just leave it fallow for several months.

what really scares me is even worse. For a while when these clowns were sick - before they died, I felt bad for lindsay, its her tank. So I put the clowns and anemone in my 300G systems refugium. So her tank is empty. I think I will effectively kill this bug now with no host for a prolonged period. However, now I'm freaking about my 300G. Lol. I have a Melanaris Wrasse that has had a couple little spots on his fin. As always it is so active the fish does not seem to be bothered. It just doesn't go away, and I don't see it unless I am really looking. So the uv is doing the correct gallons an hour. I really want to add because that uv is the biggest coralife 36W. It was on the 120, but now I have 300G. I am even thinking of doubling that unit. Putting another connecter so it has longer water passage through the twist. I noticed with a new bulb, my water is very very clear. Now with 30G not as clear. Well get through this. I just keep thinking I might have infected my reef. Whatcha think? I think I am over reacting.

I have no idea if you brought the parasite over to your other tank, but i do know UV is suppose to be one way to prevent it. But its suppose to kill your fish pretty fast, by the time you see symptoms its usually too late so i would guess that your wrasse has something else.