ich questions at hospital tank

[e46er]

ok my tank has ich it came in on a hippo tang

so now i have 2 clowns a flame angel and a foxface who have a few spots i know its worse in the gills

so im setting up my old 20G for a hospital tank i plan to treat with seachem cupramine
#1 so will all 4 fish be ok in a 20G for 6 weeks...............they all get along great but its also in a 120G with lots of caves?

#2 i have some algae problems in the 120 so im thinking a 3 day blackout and with the phosphate reacotor running with just a clean up crew it should subside i would think, ya or no??

#3 with just the CUC in the 120 in 6 weeks time when i add the fish back will this not create a mini cycle or will the bacteria survive that long??

#4 i should leave the DT running normally for the 6 weeks so coraline algae growth doesnt stop correct?

#5 what can i do to insure the clean up crew survives they havde a good amount of algae to eat now but in a few weeks in may be diminshed?
thanks for any input

Kent

Lesson learned From now on QT everything for 6 weeks