Slow coral growth.

Slow SPS coral growth.

Trying to make an effort to get my tank more stable.
Except for my Idaho Grape most of my SPS seem to grow slow or not at all.
All the normal params are in order so I'm trying to figure out some things that are wrong with my tank.
Lights= 2X 250W 14k SPS blue life bulb, 4X 65W 420,460 spectrum actinics. (7-8 months old)
SPS are directly under the lights.
Flow= 2X 1200GPH K4's, 1 2200GPH K6, Around 700 GPH return. Total 5100GPH(180 gallon tank)... not enough maybe but I've had good growth in the past with less.
Supplements: Calcium chloride, Was using Magnesium sulfate now using Magnesium chloride, Soda ash.. was using Kent marine dkH buffer(the powder)
NO3=0
PO4=0 on API test. (just got a low range Hanna instruments PO4 meter.. will measure tonight)
Nitrite=0
Amm=0
dKh=ranges 7-9
Calcium 380-450
Mag=ranges 1300-1500
Some things I suspect:

1. Temp swings. 3-5 degrees per day.
2. PH swings.. nothing too crazy maybe from 7.8-8.2.. but I just recently got a good PH probe.. so it seems like If I put a couple table spoons of Soda ash to raise my alk it may be raising it too fast. Then it drops slowly over a couple of days. Just switched to pure soda ash.. was using kent marine dkH buffer.
3. As mentioned above alk swings.
4. My biggest suspect... PO4. I didn't run a GFO reactor for a few months since my algae scrubber should be absorbing PO4. It has always read 0 on the card but from what I've been reading lately these cheap PO4 cards only really tell you if it's super high. The GFO reactor has been back up for a couple weeks now.
5. I didn't do a water change for probably about 6 weeks and I think the ionic balance got off from the Mag sulfate and calcium chloride I was supplementing. Back to changing water every 2 weeks til I figure out what's up.

I may double up on the GFO if it doesn't look good after I get a real test done.
Also I may get a calcium reactor soon so the alk, and Calcium will be more stable.

I just got a controller (RKV.2) so I hope that will help me keep the temp. more stable.
Some corals like the Tyree pink lemonade and montipora setosa haven't grown at all in about 8 months. They are known to be super slow growers.
Most LPS coral seem to be just fine.

 

All of your parameters look fine. Pretty much the same thing I have but with a wider temp swing, but I doubt it will do much.
Here's the things I would think:
Water change size? You will need to do something for the trace elements if they are small, as the bulk magnesium and sulfates don't contain much of them.
And are you running carbon and a UV sterilizer? You need both with a turf scrubber long term. The turf algae releases various spores and oils in the water that can do everything from yellow the water to inhibit coral growth.
Bulbs are close to needing to be replaced.

 

Thanks for reply. I do run carbon 24/7 but no UV. Can't wait to get home and see where my phosphates stand.

 

Oh the water changes are normally 30 gallon. But the last 2 were 60.

 

i was having a similar problem i determined that it was my 14k mh so i went back to a 10k and now they are growing fast

 

I don't think your lights are putting out enough light anymore for these guys. I checked the par under my 400 watt sps 14 bulbs about a week ago and my par was at about 175 on the bottom of the tank. I am still running those sps bulbs but i'm getting ready to make the switch to xm 15k or radiums. These sps bulbs are very very pretty but extremely weak

 

yeah what he said

 

Ok.. It may be bulb change time then. I checked PO4 on the Photometer tonight and it came up as .02... so I think that is excellent . Looks like that algae scrubber is really soaking that up so back to looking at other problems like the lights and trace elements. Sigh.

 

yeah, I was disapointed when I put the light meter in my tank. I was expecting so much out of these bulbs because of the way some of the people on this site hype them up so hard. Are they beautiful, yeah it's one of the nicest looking bulbs I have seen but if I am only getting these numbers with 400's I couldn't imagine how low they would be out of yours. BTW, we tested these bulbs in the frag tank at the LFS where I work and we were getting up in the 190's in about 6 inches of water with brand new bulbs. I think they do fine for the first few months but I think the color and strengh take a strong shift

 

Which PAR meter are you using?