PO4 All Over the Place

[JPK_Esquire]

My PO4 was between .09 and .17 for the last six to 8 weeks (tank is approximately 6 months old). I recognize this is a little high, but I want to avoid Dinos at all cost, so I am shooting to keep PO4 around .07-.09 (I.e., just a tad elevated). Tests have been performed with a Hanna Phosphorous ULR (HI736).

I added 12 corals about 18 days ago. I've had a late algae bloom (uglyphase), I think because I left the lights off for the first 4 months. I dosed Microbacter Clean last Monday. Regular weekly water change (20 gallons) last Tuesday. PO4 precipitously dropped from .11 (8/7) to .03 (8/13, last Thursday), to 0 (8/16). I tested a couple of times to make sure it wasn't a false reading, and zero three times. I then turned off the skimmer in an attempt to raise PO4 back up. And....yesterday morning (Sunday, 8/16) PO4 was back to .15. I turned the skimmer back on yesterday, and this morning (8/17) PO4 had dropped back to .04. It appears I have some diatoms, and even some Cyano growing so the low phosphates is puzzling. Also, I find it very hard to believe that turning my skimmer on and running for one day, dropped my PO4 by that much in one day.

One final note: After I saw the drop in PO4, I increased feeding from 1X a day (in the morning Rod's Food), to 2x a day (Rod's in the Morning, Neptune CD Crossover in the late afternoon).

Questions: (1) Can my skimmer be THAT effective (seems unlikely), (2) could the diatoms and cyano be consuming the phosphates, (3) should I do something about the diatoms and cyano, or let it ride for another week, (4) long-term, if the skimmer is THAT good, I suspect I should be doing some phosphates and nitrates, and (4) what else am I missing?

Other tank parameters:
Alk: 7.0-7.4 (raised to 7.8 this morning with Bicarb)
Ca: 405
Mg: 1420
Salt: 34.8
NO3: 12 (was closer to 20 until about 10 days ago)

 

[loui]

I think you are putting to much into phosphates and chasing numbers. Do the corals look good? if so stop turning things off and on and let the tank run its course. Dinos has nothing to do with high phosphates most would argue that we get dinos because our water is to clean and the dinos has nothing to compete against it. I think the biggest mistake made to new aquariums is chasing numbers and not letting the tank find its comfort zone. Keep doing your water changes and let the corals and fish tell you when something is wrong, make small adjustments and don't panic when something isn't perfect.

 

[JPK_Esquire]

I think you are putting to much into phosphates and chasing numbers. Do the corals look good? if so stop turning things off and on and let the tank run its course. Dinos has nothing to do with high phosphates most would argue that we get dinos because our water is to clean and the dinos has nothing to compete against it. I think the biggest mistake made to new aquariums is chasing numbers and not letting the tank find its comfort zone. Keep doing your water changes and let the corals and fish tell you when something is wrong, make small adjustments and don't panic when something isn't perfect.

Solid advice. My only concern was when the PO4 hit zero. Corals looks good except for a ZOA that was open and is now shut (I think it wants more flow). But all other corals look good, fish look good.

 

[loui]

The Zoa is probably closed due to the adjustment for ALK

 

[JPK_Esquire]

Been shut since I moved him, before adjustments to ALK. He was open and happy sitting in the sand, and then I moved him up onto the rock and out of direct flow. Closed and has been closed for about a week. I thought maybe since he was moved closer to the powerhead (slightly under it) but not in the direct flow, he was getting too much flow, so I moved him to the side of the tank where he isn't getting the direct flow at all. Still closed. Another Zoa colony about 8 inches away, is open and looking great. I am going to let the closed one sit where I have him for a few more days, and then move to more center of the tank if he doesn't open.