Posted: Wed Dec 02, 2009 5:42 am
It sounds like you might just have a planaria bloom. You could be overfeeding your fish - when there's a lot of planaria it means they're passing right through your fish's digestive tract.
They're really not a huge problem as they won't harm your fish.
I'm not sure if arowana will eat mosquito larvae or not, but I personally wouldn't want them in my tank! Try to put in some fish to get rid of them. How big is your arowana? If it's not big enough to eat large guppies or killifish, you could try those.
Edit: Sorry I just saw how old the first post was - got bumped by the person before me and I assumed it was a recent question.