You might want to do some research of your own, but I have used a FW dip on my seahorses as soon as I see them rubbing.
your angels are differnt, so the time may vary.
This is what I do for my SEAHORSES. Please do additional research.
Make fresh RO Water in a container large enough to hold the seahorse.
Adjust the Temp to match the temperature of the tank.
Adjust the PH to make sure it matches
Gently put seahorse in container, set timer for 15 minutes.
Sit and watch the seahorse. Usually they spaz out for about 30 seconds when you first put them in.
The settle down, and I continue to watch them. If the spazing doesnt stop after 60 seconds I abort, and put them in the QT tank, with a salt level of 1.018 after proper acclimation.
QT Tank is equipped with UV Sterilizer that I run for 1 hour on 1 hours off etc, to keep the temp from getting to hot.
If the do not react badly after the first 60 seconds, I continue to watch, at the first sign of them thrashing around, I take them out. It usually only takes about 8 minutes to start killing the parasites, 12 minutes usually really helps the guys out.
15 mins is max I would personally subject a seahorse too.
with preferance being 10-12.
in extreme cases, I will repeat every 48 hours.
At least with the seahorses here are some of the things I do to help them get over it.
1. Lower tank temp 1 degree per day, untill it is at 68 degrees F.
Bacteria grows faster at higher temps. Lower temps slows the growth and gives the guy a chance.
2. in a QT tank, run the salt at 1.018, acclimate as normal, leave them in there a few days.
2.5 UV Sterlizer - kills parisites and bacteria.
3. Garlic in the food, as well as other vitamins such as selcon, vita chem etc,
I wish you luck in your endovers.