Low ALK usage

[hkgar]

I have a 180 with SPS & LPS. My ALK usage is between 4 & 6 PPM per 24 hour period. I am monitoring this because I am lowering my ALK fro 9.5 to 7.5.

I know that that slow drop is good for the corals but it seems to indicate that the corals are growing, if they are, very slowly.

Phos .05
NO3 1.0
CA 440
Mag 1325

What could be the issue(s)?

 

[Albert184445]

How many corals do you have in the system? If you have just a few frags compared to large colonies the alk consomption is going to differ

 

[hkgar]

Here are a couple pics to give an idea of corals






The tank was started 2/1/13 and I started adding corals in July, 2013.

 

[hkgar]

Anyone want to offer some suggestions?

 

[PaleHorse]

your tank is growing... needs more. as your coral grow you might need to dose more. tank looks good!