Moving from one tank to another.

[marie]

When I moved my 2 smaller tanks into the 175g tank, I put all new salt water, new sand and dead base rock in the big tank and then let it cycle with cocktail shrimp for a few weeks. Then I spent a day moving everything over.
I first removed all the fish and put them in buckets, then cleaned all the algae and rinsed the rock off really well in the old tank water before placing in the new tank.
The move went well and I didn't lose any corals but for some reason all my fish came down with marine velvet 2 weeks later and i lost most of my them before i could get them all into a hospital tank and treated.
My suspicion was that my yellow tang was the carrier because he was in the same tank as a majestic angel that died a few months earlier of velvet. The yellow tang, clarkii clown, and 3 chromis were all that survived