Acropora polyp extension problems

[billdsl]

Hey All

I have an issue with polyp extension on my acropora's. I have several different type's and all have this issue at present, excluding a new colony of milepora just added.

Basically i think i had a spike of some kind that took out one colony and seems to have effected the rest, and after several months the problem hasnt eased.

All of the acro's I have used to have awesome polyp extension during full lighting, now they get none, lights on or off, still seem to be getting some growth but just no pe.

Ive asked a few people locally (who id consider guru's) who suggest its fine but I really would like to find a solution.

Tank info:
- 4x2x2.6 plus sump (approx 450L)
- 2x150w MH, plus 4x18w pc actinic, running for approx 14h per day
- 1x12,000lph tunze for circulation
- Decent sized protein skimmer, purigen, carbon, taxifolia in refugium
- Readings
- Nitrate, Nitrite, Ammonia: 0
- PH: 8.3
- CA: 420
- ALK: 7dkh (bit lower than normal, generally runs at 7.7dkh)
- PH: between 0.03 & 0.1 (unsure with salifert colour chart)
- Top up: RO/DI, with kalkwasser
- Tanks been running for nearly a year

A pic of the tank atm --> http://i9.photobucket.com/albums/a77/billdsl/4ftTank/Full Frontal Photos/FullTankOct06.jpg

Im sort of holding off going with a lot more sps till i get this sorted, and am about to replace the 150's with 250's.

Any thoughts/idea's on what I might be able to do to get my pe back? If any more info is needed let me know.

Thanks
bill

 

[prodman]

I notice a loss in Pe in my tank if my dkh drops below 7. You might want to raise that back to 7.7-8dkh. Also check for redbugs or a nipping fish.

 

[LobsterOfJustice]

Is that a flame angel I see in there?

Even if you never see it nip, my experience is that, for some reason, Acropora wont extend in the presence of angels. I have a majestic in my reef, he NEVER nips anything, yet I get 0 PE during the day (even milles), but plenty at night when all the fish are sleeping. I have heard that many others experience this as well.

 

[onehundred20]

id say get you alk back up to 8

 

[Serioussnaps]

ALK!!!!!!!!!!!

also give them good flow

 

[billdsl]

thanks for the comments guys

the flame is only quite a recent addition, i had this problem for several months prior to him going in, so its possible he's annoying them but think its probably something else as well

ill definitely bump the alk up, flow's around 20x atm, this not enough?