Sorry to hear that your snapper didn't make it.
In your case especially, I would not recommend using damsels to cycle the tank. Ich can only survive for limited periods without a fish host available. If you allow your tank to run fallow by removing all fish to a QT then all ich parasites left in your tank will die out in within 3-4 weeks.
Make sure that you keep ich out of your QT tank as well, use freshwater dips or medications to treat it (move your inverts out of your QT first).
If your goal is just to banish the marine ich, I would not completely take down and re-cycle your tank if I were you. I would keep your lion in QT for about a month and only keep inverts in your main tank while you let it run fallow of fish for 4 weeks. With no inverts in your QT you will be able to medicate your lion if needed. But on the other hand, if there are other changes you want to accomplish by taking everything down and starting from scratch then this is a good opportunity to do it.
Finally, be prepared for frequent 25% water changes in your QT while your lion is staying there. There's no biological filtration established in your QT so ammonia levels could rise quickly. I'd just keep a constant tub of fresh mix saltwater running with a heater and extra pump and do small volume water changes in your QT every day or two.
In your case especially, I would not recommend using damsels to cycle the tank. Ich can only survive for limited periods without a fish host available. If you allow your tank to run fallow by removing all fish to a QT then all ich parasites left in your tank will die out in within 3-4 weeks.
Make sure that you keep ich out of your QT tank as well, use freshwater dips or medications to treat it (move your inverts out of your QT first).
If your goal is just to banish the marine ich, I would not completely take down and re-cycle your tank if I were you. I would keep your lion in QT for about a month and only keep inverts in your main tank while you let it run fallow of fish for 4 weeks. With no inverts in your QT you will be able to medicate your lion if needed. But on the other hand, if there are other changes you want to accomplish by taking everything down and starting from scratch then this is a good opportunity to do it.
Finally, be prepared for frequent 25% water changes in your QT while your lion is staying there. There's no biological filtration established in your QT so ammonia levels could rise quickly. I'd just keep a constant tub of fresh mix saltwater running with a heater and extra pump and do small volume water changes in your QT every day or two.