rust

[acasden]

My tank is over 2 years old, recently have seen what can best be described as "rust" on the rocks, not getting nearly as much coraline algae as I was. It has been several weeks and not getting better, mostly located low down where flow is not as good obviously. Not sure if diatoms or dino but doing extra water changes etc, phosphate 0. all other parameters stable for 2 years.

Any thoughts?

 

[Anonymous]

How long has it been since you changed out your light bulbs?

 

[acasden]

about 3 weeks ago and lowered the time and then a week later gradually increased. I had looked into that and heard it could be source. Increased water changes also,

What concerns me is less purple coraline algae and more of this broun/rust colored stuff on rocks?

 

[Anonymous]

Well, some coraline doesn't like increased lighting, it could be reacting to that. Also its tied to Ca/DKH. What is your water testing at? Do you supplement Ca?