I had a very bad experience lately. My 21 inch silver Arowana had slime and white spots and was not feeding for about 7 days. He had a 17 inch Motoro stingray (female) for company in my 600 litre bare bottom tank. Stingray was introduced when she was just 8 inches and both lived peacefully. I got a bottle of Ocean free liquid (Slime.white spots & Velvet away) and put in the required amount as per their specifications. Within 10 hours the Arowana started jumping like mad and I got a call from home saying that the stingray has turned over, rushed home and changed 90 % of the water but by then then the stingray had died. I know it was the greatest mistake of my life that I didn't shift the stingray to a different tank. I found some white thread like objects when I was cleaning the top filter the next day and I suppose they must be the left out worms from my Arowana and some of these the sting might have eaten causing her death. Please advice friends. The only silver lining is that after 4 days of treatment the Arowana is now fine and feeding.