Sounds like you are on the right track as far as the 24gallon goes. Is the temperature and flow in the QT/hospital tank good?
What specifically is the stress reducer? Many chemicals that help fish fight off disease harm invertebrates. Corals, clean up crews, feather dusters, pods, and countless other things in our reef tanks can be harmed by many things that would help fish in a QT or hospital tank. This is regardless of what any miracle cure package may claim. I can’t tell you how many tanks have been ruined in the past by “reef safe” chemicals.
You may want to read up on adding vitamins and fresh garlic extract to the food for a little bit just as extra measure. May not be necessary at all, but could help give them the extra boost they need.
It’s likely a lot easier to keep the parameters and everything in check with the display tank then it is with a little freshly made up QT tank. You may want to keep the clowns in their for now. I realize there is still a bit of mystery as to what might have been killing the animals, but a bare empty QT tank can be hard to keep balanced.
I’d look into something better then just a generic multy pack. There is a good chance none of your fish eat the squid so your essentially throwing a fourth of what you are paying for away, but it’s worse then that because it’s adding crap to your tank. Just try sometime to add a little squid by itself and see if a fish actually eats it and swallows it and goes for more. There are some fish that will eat it, but I have found an a lot don’t.
Keep us up to date. Best of luck to you and the animals.
Temp and flow in the qt is good, put in a little powerhead and heater from my old 3 gallon setup.I only used the ich meds in the qt but added the stress reliever to both. Not sure which brand off hand but it says its good for adding new fish and so on, claims its safe for the tank. I’ll have to look at it when I get home and let you know which one it is. I have a flake food that has garlic added that I can feed with the frozen, I will also see if I can eliminate the squid once everything is back up and running.
If you think that ich may have shown on the damsel because it was already stressed/it’s immune system was compromised then it may be worth it to add Vitamin C to their diet which “is associated with improved tissue growth and with aiding the immune system”.
Meanwhile if you get in the mood to read up on fish disease and really cross some things off the list and narrow down specifically what is going on or if you continue to have problems look into reading what Lee has to say about this sort of thing. Another great person to turn to is Kelly Jedlicki who moderates a forum over at MarineDepot.com These two know more then 99% of hobbyist would ever care to know, but just give them the curtsy of reading some of their stickies at the top of their forums before bothering them with a question they have already answered.
Activated carbon will do more harm then good when left in for two months. That was certainly poor advice. Once a month I pretty much consider required, but very lazy. Twice a month in a low nutrient system may be ok. Once a week would likely greatly benefit most aquariums, but that really depends on your bio load, types of foods, other forms of filtration and maintenance and many other things. KEEP IN MIND activated carbon will remove many medications from the water. If you are attempting to treat the hospital tank leave carbon out until after the treatment and after a water change.
Hope it all works out for ya and the remaining three pull through.