Very surprised: new carbon made green water go away

[hashbaz]

I just changed the filter cartridge (the kind with carbon inside) in my HOB for the first time in several months. I was surprised that this cleared up my water. It had been slightly green before. I think carbon only removes chemicals, and I am guessing that the green was from water-born algae. Does anyone know what caused the green algae and why new carbon made it go away?

I know someone will ask about water parameters so:
PH 7.6
ammonia 0
Ites 0
Ates 15
GH 8
KH 4
My tank is fully (if not over) stocked with HOB and UGF. It has several plants, 40Watt fluorescent. I lightly dose iron potassium and trace.

Any thoughts? TIA

 

[deeni0z]

carbon removes heavy metals. it might've removed the iron.

 

[Toirtis]

I agree...may have also removed some extra nutrients floating about...just enough to stop the algae bloom.