This is a discussion on Brooklynella hostilis within the Saltwater Fish Diseases forums, part of the Saltwater Fish and Coral Reef Tanks category; -->
wad r the symptoms of velvet...
notice my emperor is breathing fast....
sometime swimming at the top.....
most of the time at the swimming ...
Considering the many problems with your system, there is no way to medicate those fish in the main tank.
Can you post pictures of your angel so we can get a better idea of its problem?
The best thing to do is to get the main tank fixed as quickly as possible. If that doesn't happen, one animal at a time is going to have problems, and there isn't anything more to do about it than to get them into a proper environment.
In the mean time, if you set up a quarantine tank, a sick fish can be moved to the quarantine tank for needed treatment. Please be aware that moving a sick fish to a quarantine tank and then returning it to the current main tank is only going to bring the problems back.
You might want to consider getting rid of some of those fish until you have a proper environment set up and ready for them.
Please be forewarned, Paraguard contains malachite green, which is not safe for all fish. That is a very harsh medication. If there is ammonia or nitrite present, or nitrates are over 40, malachite green can be toxic.
UV alone will not kill all parasites, and won't do anything for parasites that are on a fish.
The way UV works is that the tank water is circulated through the chamber, which exposes it to the UV light. Water that passes through the UV chamber will then come back into the tank "clean" of all those little nasties.
How effective a UV unit is depends greatly on the amount of circulation in the tank. Parasites will tend to live in sand beds, on rock, and on the fish. Unless they are in the water that passes through the UV, they would be completely unaffected.