calerpa wont grow

[rtstrat01]

i have a light ficture with two screw in pc bulbs, i have a 6500k at 15w and a corallife 50/50 that is between 10-15w, so why is my calerpa not growing, do i have the wrong spectrum, my calerpa is turning light green and white and has not grow any in like a month and is starting to lessen

any advice

[graveyardworm]

Sounds as though there isnt enough nutrients in your water to support it. Have you tested your water for NO3 and PO4?

[rtstrat01]

my N)3 is at 10, and PO4 is between .5 and 1. and i do have hair algae in my display

[graveyardworm]

I dont believe your lighting is insufficient, I grown caulerpa under less light than that, growth wasnt impressive, but it did grow.
One other possibility could be low iron, iron is a limiting nutrient for caulerpa. How often do you change water and do you dose iron?

[Samala]

Ah, but how deep is this tank that the Caulerpa is in? That amount of light over a larger tank may not be enough.

Iron is a possibility. A few drops would let you know if that was the problem. Caulerpa's respond pretty quickly to supplemention of Fe.

>Sarah

[rtstrat01]

well my sump is on my 29g not sure how many gallons the sump is, but the refugium is only light 8x10x6, so its not a depth thing, like i said the tank is 29 and i do a 5 gal water change every weekend, and its saltwater i get from my lfs so i dont have to deal with mixing, as for iron, i have never been told calerpa needs iron, whats the type that is recomended and how often should i dose on my 29.

[graveyardworm]

What type of caulerpa, and how long have you had it?

Also how deep is the refugium?

edit: Sorry I think I misread your post the dimensions listed are the size of the fuge?

[rtstrat01]

well i have some grape, maybe about two weeks and its turning white, and the other kind not to sure but i have had it for about a month, its still a light green, but hasn't gotten any bigger

[graveyardworm]

It probably wouldnt hurt to try dosing iron and see what happens. I use Kent marine iron follow the dosing instructions and you shouldnt have a problem. Although I would start with half the recommended dose to see what happens and slowly work up to the recommended dose.