You're reminding me of what I had to do months ago. Had the exact same trap. We had a super long line extended on to the door to the tank, after we caught the chromis no one else wanted to go in. It took months to get all the fish out and to let the tank fallow, worst of all was when I put the fish back in after medication the ich came right back. I used CopperPower. Fish did not do as well in quarantine (although the ich cleared) my powder brown became a very picky eater while in quarantine and definitely was not as fat as he is now. The corals suffered too without the fish. I lost my yellow tang due to stress just from catching and transferring, :( he went in to a 20 gal QT with freshly transferred tank water and an already cycled filter with a couple elbow pipes and it wasn't enough. I quickly learned that stress is major factor that can kill within 24 hours so went and bought big fish caves and more pipes so they could feel more safe in QT. We called the stacks of pipes the chromis hotel. The fish seemed to appreciate it a lot. I wish had done better before trying to transfer the yellow. In the end I ended up getting a UV sterilizer and haven't seen any ich spots since I dialled in the flow rate. The worst fish to catch was the little neon blue goby, who refused to go in the box no matter what I did and was feasting on excess copepods. I ended up having to drain the tank for a few minutes just to catch the little bastard. In hindsight I wish I had just bought the UV to start with. The amount of filters and tanks and water changes it was such a time suck and wasn't fun for me or fish and in the end all for nothing. I hope you catch em all fast at least its not many. I have a Vecton unit now but any unit can work just need to achieve level 2 sterilization to rid the parasites. This video was what helped me come to the conclusion that UV could help my situation ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CwcUVmfEMbY.html If you still have problems after you put the fish back I would consider it, I never used an oversize unit, the standard sized unit seemed to work literally overnight was a huge difference, it took a while to dial in the flow rate to get to 0 spots (I would see the odd one on my powder brown every now and then) but my unit is barley large enough to reach level 2 for my tank size so that's why. After getting a proper sized adjustable flow pump for the UV unit, no ich spots. Sorry for the long ass read, hope some of this is helpful.
