Caulerpa "Grape" algae turning brown

Now I know that I have a problem if my macro algae starts turning white. but what about turning brown... I have a piece in my fuge sump that is turning brown.... any input....
all parameters are at 0 and 8.4... I have been killing(removing) the red velvet / blue green algae/bacteria...
....but does this sound familiar for this to turn brown???

Thank you

 

perhaps your low on iron?

most fresh plants turn yellow when there low on iron, tho

what type of lighting do you have?

 

I am using a 16w 6500K CF bulb in a with a clamp on unit...

 

whats the size of your fuge?

 

10sump with about 5 gallons for the fuge...

 

im assuming the light is right above the caluerpa so you could say it gets 3wpg

could it be a lack of nutrient(ie the other algae is using it all)? macros do like nitrates, ammonia, nitrites, thats why we use them to remove nitrates

what about your ph, alk, calc, magnesium, im not sure how much bearing these have on the caluerpa but some macros do use them.

 

my PH is at 8.4. I havent started testing for mag or alk. I got the grapes to help remove the bad to assist in clearing the algae issue... as well as my removal..... I dont thing that the mag or alk would do any of that but you never know. I just was wondering what could be making it do this. I changed all my filters( phosphate, poly as well as my carbon bag) today just ot be sure. I also cleared the algae on the acrilyc.....I also am using a protein skimmer...

 

i think it may be your phosphate filter, plants need phosphate to grow. i think its because your water is too clean thats my guess, but you could wait and see if john maloney from reefcleaners.org gets on, hes much more expierenced with marine plants then me.

 

That would be a first. my tank is too clean.... who would have thought....

 

Anyone else have any input?