Help ID Algea - sponge turning red

[brucelee90]

Hi guys, this red slime is wiping out my QT again. The sponge filter in my HOB suddenly turned red today and my QT has red slime growing on the glass. Is this dino?

Some other data:

1. The water has a very pungent smell resembling rotten seaweed.
2. Phosphate level is normal, although I'm overfeeding my fish for its recovery.
3. I dosed some prime and Fritz turbo start 900 yesterday to control the ammonia level (not sure if this correlates to the bacteria bloom)

I did a large water change and put a airstone in it but I doubt it'd help to control the bloom. Help!

 

[brucelee90]

I tried to wash my sponge many times but failed to get rid of the red stuff.