next steps with Velvet

[korted842]

started my first reef tank roughly 4 months ago. Over time I introduced a pair of clowns, a long nose hawk, lawnmower blenny, Midas blenny, and a small blue eyed tang. I had a small Valentini puffer that I learned loves to snack on coral and I had to return him I did notice what almost looked like ich or velvet on his body and my my cleaner shrimp would always be cleaning him. I brought the puffer back to the LFS as I did not I am extra tank to quarantine. Thay took him but about a week later velvet started to appear on the tang and the midas blenny. I began dosing polyplabs medic to almost no effect. About a week later the clowns were gone. All of the fish that died were covered in small white speckles and the tang had started to get rashes or loose tissue as it got worse.
thw long nose hawk and lawnmower blenny seem to not have any sort of visual parasites on their fins. The fish have been doing well it seems as far as health.

the tank is a 40 gallon bow front

temp at 79
Salinity at 1.025
Ph 8.1
nitrate 50 ppb
Nitrites .4 ppm
Phosphate.20-25 ppm
Alk 9 dkh
Cal 440
Mag 1300

so I’m cycling my next system a 125 gallon tank and don’t know what to do if I put together a 20 gallon qt tank would they be able to live in that for now while I treat
Also how am I going to get it out of this display tank

would it help if I removed all fish and restarted my dosing of medic to the tank
Or would I still be
Stuck for 70 days until I can put fish back into the aquarium?

 

[korted842]

Also if I were to transfer the live rock from this tank would the parasites be inside the live rock? I’m assuming they probably would.