I have 2 spotted pictus, 2 irradant sharks and 4 tiger barbs in a 20 gal tank. Yesterday I cleaned (vacummed with gravity flow vaccum) and did a 50% water change taking care to keep the water at same temperature and treat for chlorine. About 10 minutes after I was done my catfish started hiding in corners and acting strangely. I turned on fluorescent light and my worst fears were confirmed. All the sharks and catfish had the white spots. I immediately treated them with that green liquid and took out the carbon filter. My catfish are not eating right now. Is it possible that the stress I created by poking around in the rocks casued the ick. Can they get it that quickly. Any help on this subject will be greatly appreciated. I lost my entire batch of fish about 2 weeks ago so thought maybe upgrading from a 10 to a 20 gallon tank might help. My water tested ok. A little high on alkaline.