Low PO4 & Polyp Extension?

[Overboard]

Hi,

What affect does low phosphate have on SPS polyp extension? I have read several threads that mention that high phosphates diminishe PE, but what about low?

I ask because my SPS have inconsistent PE. Some millepora and others have fair PE, but some, like my German Blue Polyp, have nothing. All corals have at least a little at night. All corals are growing but on most, the colors are pale.

The system has been up for 2 years. Hanna PO4 meter always shows zero, and Salifert NO3 test shows zero. Doesn't seem right to me. i tried to feed the corals daily for several weeks and the tests still show zero. No change in the corals I have GAC and GFO reactor and dose vinegar, but I tried feeding so heavily the tests should show something.

I have strong water flow (tunzes & closed loop) and a combo of 400 watt MH and LED lighting. Alk around 8.0.

My guesses are either (i) the test readings are wrong and I actually have high PO4 and NO3 (maybe leaching from my DSB) or (ii) the readings are correct and the corals are starved.

Input?

Thanks!!

 

[Blueline12]

Sounds like starvation if the Hanna shows 0 Po4 but color is pale. Try amino acids or some fauna Marin products to feed them.

 

[mrbigshot]

i have 0 po4 but get good polyp extention day or night. i feed the tank every few days about an hour before lights out. im using feeder food from reefcleaners because i cant find my reef chili or coral frenzy. lighting is 2 d120 leds on a 75g. flow is 2 mp10w es on reefcrest @ 100%

 

[jpacker1508]

The first thing I would do before I changed anything is try a different test kit so you really know what is going on. Then after double checking myself I would take a water sample to a trusted fellow reefer to confirm. Then and only then would I start correcting any issues. Do you back up your Hanna with actual tests? What is your PH?

 

[Overboard]

I'll double check the Hanna with the Salifert test I used before. I just never found it much help either.

Backed off the feeding schedule, upping the water changes and keeping the GFO fresh. I'll give this a try for a few weeks and see what happens. I would hope to see some improvement if phosphates are the issue despite the test results.

Thanks!