Why Won't My Coral Grow

I run 175 watt metal halide 14k bulbs 10 hours a day, my phosphate wont go less than .5 even though I constantly run a phosban, my ph is 7.9, cant seem to raise it, my alk is 3/10.5, calcium is 450, magnesium is 1300, nitrates controlled by hang in refugium with chaeto and one mangrove pod that i just put in there last week. The tank has been set up for over a year and coral growth is really really really slow. I do admit that these conditions have been kept perfectly for about 6 months and may have differed preciously. The most growth I have had is 1 head of candy cane coral splitting into 2. I have 2 koralia 3's, 1 on each end mid way facing each other and a seaclone just upgraded to a hob berlin xl with a ca1800 pump, not quite sure how to break it in but have the pump runnin and the valve open all the way. Its been three days so still waiting. I'm hoping the skimmer will make a big difference but any suggestions/questions would be greatly appreciated. This is my first post as I am new to this site. Thank You

 

What corals do you have? How old is the bulb? Luna

 

Also, do you do WC? Luna

 

What have you tried for raising your ph?

 

The bulbs are about 8 months old, I do 20% water changes every month. As for PH, I don't know what to do to raise it without affecting alkalinity. I tried using 8.4 by the seachem aquavitro line but lost a few inverts and that raises my alk. What can I do to slowly raise ph without bothering alk too much. Even with a 7.9 constant ph I would expect some growth considering its closer to natural seawater..........

 

Does the tank have to be established and constant for a certain amount of time before the corals start really growing. I bought a toadstool and its just been glazed for 3 weeks and only showed polyps day one and one day in between and at night it has some kind of stringy web things it extends. Sorry for all the questions and thanks for the prompt responses.

 

Im a little hesitate on recommending what am about to recommend, but all of the ppl that I know of who sell corals for a living keep their numbers higher than what you do. I do to. I dont know how exp'ed you are or if you know how to fix any problems that may occur. I keep my numbers as follows.
Mag......1500
Cal........450-480
DKH/Alk......12-15

My corals grow pretty good and have 2x and even 3x in size within a couple of months. Having said this, they will not grow over night, so expect to wait a couple of months. Maybe part of your trouble is that you lack patience;D



[SCROLL]Luna[/SCROLL]

 

Ph is not going to make your corals grow. I had the same problem not to long ago. If my ph reached 8.0, it was a miracle. Im assuming that your house is closed up, no freash air coming in. What I did was to leave open a window(1"-2") that was close to the tank and my ph is normally between 8.1-8.3. The problem with your ph is that there is too much Co2 in your house. Luna

 

Try this experiment. Take a glass of tank water and place a air pump with an air stone in it for .30 mins. Test your ph. Now do the same thing outside and see if you get different readings. If am right, your outside reading should be much higher than the inside one. Luna

 

Also, you never answered which corals do you have? luna